From Glitchtale Wiki

Wing Din Gaster
Gaster infobox.png
Soul/Trait Boss Monster Soul
Species Skeleton Monster
Gender Male
Status Alive
Theme Vantablack
Voice Actor Zedrin

Dr. Wing Din Gaster was a member of The Wizard Council before the events of the Human-Monster War, in which the monsters were sealed beneath Mount Ebott. Wanting to free the Monsters from their imprisonment, the royal scientist focused on soul experimentation, which eventually led to him falling into The Void. For an indefinite amount of time, he remained trapped in limbo, forced to watch every timeline simultaneously. He is eventually rescued by Sans, one of his two children.


Gaster is a male Boss Monster that has a skeleton-like appearance. His two eye sockets have permanent scars coming from them. Gaster typically wears a large black coat over a lighter shirt, with brown pants and shoes. He sometimes wears a white lab coat when performing experiments inside his lab.

When triggering magic, his eye color depends on the status of his two children. When Sans and Papyrus are alive, he'll have both a red and light blue eye. If one were to die, that corresponding color will fade away. If both were to die, his eye color will return to its original purple.

Appearance Gaster.png


Gaster's personality is initially that of a cool, charismatic skeleton. He is a kind person who gives people respect, and cares for his friends and family's well-being. He is a brilliant man, capable of calculating strategies to win battles.

When in The Void, Gaster's sanity plummets to the point where he will kill anyone, including his own son, in order to return. After being rescued from The Void, many of his memories are repressed.

His repressed memories’ resurfacing adds to the deterioration of his mental state, as his insistence to avenge his son has resulted in constant failures. This buildup of rage and mistakes eventually leads to his breaking point in Animosity.

Powers and Abilities

  • Chroma Hands: Gaster has seven hands that are each able to mimic one of the seven Human traits at a time.
    • Red: Shoots a powerful red blast.
    • Orange: Spawns explosive orange bombs in a desired area, that explode on command.
    • Yellow: Rapidly fires yellow projectiles.
    • Green: Summons a green shield which consumes magic to strengthen and maintain.
    • Cyan: Fires a string used for restraint, as well as flinging the captured victim around.
    • Blue: Spawns a buzzsaw that flys out towards its intended area.
    • Purple: Creates purple spikes that damage the opponent, while also slowing the effects of healing magic.
  • Gaster Blasters: Blasters that fire powerful energy from their mouths.
  • Healing: Gaster has the ability to cast Healing on others and accelerate their recovery time.
  • Telekinesis: Gaster can move people and objects from a distance.
  • Teleportation: Gaster can teleport himself and others from one place to another in an instant. This ability is lost in Do Or Die.

Special Attacks

  • Monotone: All of the hands focus on one color, amplifying the power of his next attack by seven.
  • Duality: Gaster's seven hands merge into two giant ones, along with him obtaining a large blaster.
  • Polychromatism: The power of Duality, and the addition of seven smaller hands. It is the most efficient and least taxing version of Gaster's full power.


Season 1

Yet Darker

Gaster notes the strange occurrences in this unique and glitched timeline. Seeing this as an opportunity, he hijacks Sans' teleportation, leading Frisk to Gaster's door. After blocking the RESET button, Gaster intends to steal Frisk's soul in hopes that it will give him the ability to return from The Void. Even with Sans showing up to Frisk's aid, Gaster can easily overpower him. Sans has the idea for Frisk to give him his soul, just as he did in the previous timeline. However, Gaster takes advantage of Frisk's exposed soul and captures it, after impaling Sans with a black tentacle.
YetDarker Gaster1.png
Before Gaster can fully steal it however, Frisk refuses, and the soul propels itself to Sans, allowing the skeleton to absorb it as they initially intended. The Human/Monster hybrid proves far too powerful for Gaster to handle. Gaster desperately tries to kill Sans, as the latter effortlessly counters his attacks, leading to Gaster’s time outside The Void running out. A saddened Sans tells his defeated father that killing people isn't the right way to be restored. Gaster tries to stealthily attack Sans from behind, but is impaled instead with bones through Sans' attack. Gaster then dusts away, Sans resets the timeline, and Gaster is restored, albeit still trapped inside The Void.
YetDarker Gaster2.png

Your Best Friend

Finally able to perfect the machine in his lab thanks to the glitching timeline's errors, Sans opens a gateway to The Void and successfully restores Gaster to his former self. Gaster is overjoyed to be free and happily agrees to help the others defeat a HATE-influenced Chara. Keeping a drained Frisk protected in a shield, Gaster, Omega Flowey, and Sans all do their best against Chara, who now has the ability to mimic traits. Despite their best efforts however, Chara effortlessly defeats them with his overwhelming power.
YourBestFriend Gaster1.png
Gaster is gravely wounded when taking an attack for his son, Sans is knocked out after using his Gaster Blastermination, and Omega Flowey reverts to his flower form after matching one of Chara's massive attacks. Chara prepares to finish the lattermost off before Frisk (with his recently restored Determination) gives his soul to Flowey, along with the other six Human souls. This allows Flowey to become Asriel, in his God of Hyperdeath form, to engage Chara.
YourBestFriend Gaster2.png


Gaster catches up with many monsters who came to see the commotion at the barrier. Afterwards, when Asriel breaks it, he steps onto the surface with everyone else.

Season 2

My Sunshine

During the first month of the Monsters' return to the surface, Gaster is recognized for his scientific works and begins expanding the CORE. As he explains to Jessica, doing so will eliminate the need to pay for electricity ever again.

After the reveal of Betty's unique pink soul, Gaster begins researching in an attempt to identify it. He finds nothing, however.


As requested by Betty's parents, Gaster allows her to stay at his lab for a short time. He persistently continues researching the pink trait but is still unable to find any clue whatsoever. He decides to take a break and reads The Tale of The Twin Siblings. However, upon reading it, he finally stumbles upon the origins of the pink soul: A Bête Noire with the soul of Fear.

Upon finding this information, he is too late to warn the others, and Betty soon kills an already weakened Sans. Gaster sees everything from Sans' perspective before the moment he died and immediately becomes filled with vengeance

Do or Die

After Sans' death, Gaster immediately looks for every piece of information he can find about the "Bete Noire" to avenge his son. Upon discovering that Determination is supposedly its only weakness, he goes on a rampage within his lab, his outlook on life greatly affected.

Eventually, Frisk meets with him, and soon after, the lab is attacked by pink blobs that had been planted by Betty earlier on. After seeing Frisk struggle to defeat the blobs, Gaster believes Frisk will never be able to win against Betty, and decides to do it himself.

With the help of Alphys, Gaster has reconfigured a machine, originally designed to eliminate dangerous particles from the CORE. Its new purpose is eliminating any Humans or Monsters within the room. He explains to Alphys that the plan is to lock the doors and activate The Nullifier if Gaster loses the fight. Unbeknownst to Alphys, Gaster doesn't mean to kill Betty with the machine, but rather himself if he fails. Gaster soon battles with Betty in The Nullifier Room. He tests Betty's fighting prowess until he learns what she's fully capable of.
DoD Gaster1.png
He then puts her in a situation where she can't counter, by separating her from Akumu, and almost manages to kill her. Betty survives long enough to reveal a move she had been waiting to use until she had enough souls: Rhabdophobia. Using this ability, Betty brutally beats Gaster by stealing his magic and using it against him. Defeated, Gaster looks at the spectator window before being stabbed with a spear. Gaster is saved by Alphys and Jessica, with the latter blasting Betty away with her gun, before teleporting them both away with an artifact. This leaves Alphys to deal with Betty alone.
DoD Gaster2.png


Part 1

Gaster experiences a brief flashback of his final moments in the CORE before falling into The Void. After a failed experiment, the CORE began to overheat, and the interior began falling apart. Gaster and an unnamed monster scientist struggled to stabilize the CORE's temperature when Sans arrived to warn Gaster to evacuate. Gaster refused to leave, telling his son that everything would be destroyed if the CORE didn't stop overheating. Despite Sans' pleas, Gaster stayed behind and was successful in preventing the CORE from melting down. Unfortunately, the CORE's interior was still damaged from malfunctioning, and a section of the platform that the other scientist was standing on shattered, sending him helplessly into The Void below.
LOVE p1 Gaster1.png

Gaster and Sans both ran to escape, but a damaged pipe broke from its constraints and fell on them. Gaster was able to shove Sans out of harm's way, but couldn't save himself from being slammed off the platform into The Void. As he falls, the CORE begins to release blue plasma throughout the room, granting both Sans and Gaster the ability to teleport.

Gaster soon awakens thanks to Papyrus using healing magic. When Jessica explained that Alphys had a plan to kill Betty alone, Gaster panics in a rush to get back. Gaster tries to teleport to the scene with his damaged soul, only to lose the ability to teleport entirely. He calms down after hearing that Undyne went to save her. Gaster looks down and is surprised to see his hands covered in blood. He realizes that although Monsters shouldn't be able to bleed due to their lack of physical matter, Monsters living among Humans and eating Human-made food have allowed Monsters to gain a more physical form. With this new information, Gaster believes Undyne might attain her Undying form without melting.

Later on, Gaster is recovering on a couch while Jessica uses his control panel to access the AMD's surveillance equipment. Gaster is upset by this and questions who allowed her to use his device, to which Papyrus responded that it was him who allowed it, annoying him further. Gaster appears surprised and almost impressed when Jessica warns everyone in the city of the soul-stealing Fear blobs, and tells the Humans to seek aid from nearby Monsters that could scare away the blobs with their magic.

Soon after, Undyne returns from her duel with Betty, appearing to be unharmed physically, but stricken with guilt from accidentally killing Alphys. Papyrus takes her to a nearby room to tend to her, leaving Gaster and Jessica alone. Jessica tries to tell him that she might understand how Gaster feels and apologizes for her actions. Gaster refuses her apology and angrily replies that Jessica played a significant role in the demise of Sans and Alphys. He menacingly assures Jessica that the only reason she's still alive is due to her friendship with Frisk.
LOVE p1 Gaster 2.png

After Frisk returns from the school, he asks the two adults about the others. Despite partially being at fault for withholding information about the nullifier, Gaster tells Frisk that Alphys was “in another body bag" because of Jessica. Frisk takes Jessica to a storage room to show her something, as Gaster stays.

Part 2

Gaster is shown looking outside his window late at night, unable to sleep, reflecting on the previous day's events.

Later, Gaster secretly looks through Jessica's database and discovers that the AMD captured and contained the HATE substance that escaped sometime after the events of Continue. He goes to ask Undyne how she failed to exterminate Betty despite having Determination. Undyne explains that Betty consumed a black substance that boosted her power before she could land the finishing blow. His suspicions confirmed, Gaster snaps his pen and prepares to attack Jessica, but halts after his anger subsides. He tells her that if she had told them about the HATE vial, they could have prepared for it and things might have turned out differently. He then states to Jessica that he doesn't care about her excuses and wishes he had never met her, causing her to lose her trait.

Love p2 Gaster1.png
Papyrus finds Gaster alone in an empty room and sits next to him. Gaster asks Papyrus how he can forgive people no matter what they do to him and whether or not Papyrus ever cared about Sans. Papyrus tells Gaster that there wasn't a time of the day he didn't think about his brother, but he didn't want anyone to see him upset because others rely on him for comfort. Papyrus gives Gaster a repaired "Bone Appetit" mug. Papyrus tells Gaster that they shouldn't deny apologies from people when they have already made so many mistakes. A refreshed Gaster tells Papyrus he will give forgiving Jessica a chance.

Love p2 Gaster2.png

Later, Gaster feels Sans' sudden return and location when Betty uses HATE to revive him to fight the newly-powered Frisk. Papyrus rushes off to the scene, despite Gaster telling him to stay. Gaster then quickly gathers Asgore and Toriel so the three can follow Papyrus to rescue the others from Betty.

When the three Boss Monsters arrive at the scene, Betty uses a HATE dome to prevent them from interfering. Everyone witnesses Sans break free of HATE's control when the dome is destroyed. After Betty escapes, Toriel explains to a concerned Gaster that Sans is in some form of coma after having nearly all his magic drained, and that he might never wake up. However, Papyrus assures Gaster that Sans is strong and that he will eventually awaken.

My Promise

The others arrive home to see Jessica and Undyne being attacked by Fear blobs that managed to break in. A blob manages to stab Jessica in the chest before Asgore kills it with his trident. After hearing that she'll live, Gaster and Papyrus take Sans to Gaster's laboratory in the underground. Gaster initially has trouble remembering the password due to his memories being suppressed from his time in The Void, but remembers after a quick flashback.

Gaster immediately runs tests on Sans' body to see how he can save him, but to his horror, his computer identifies Sans as "fallen down", which means that he will soon turn to dust. When Papyrus asks about the results, Gaster lies to him about Sans' state and orders Papyrus to stay with his brother, as Gaster gets ready to return to the others. A concerned Papyrus repeatedly suggests other things he can do to help, but Gaster refuses, even going so far as to threaten Papyrus with his Chroma Hands out of stress. After apologizing for snapping, Gaster leaves Papyrus in the lab, and changes into a darker coat, before joining everyone else in the house.
MyPromise Gaster.png

Gaster brings a "Monster History" novel and begins explaining his findings, swiftly dismissing Asgore's concern for Sans' well-being. Gaster informs everyone that if a bond between Asriel or anyone corrupted with HATE is strong enough, the victim can break themselves free of its control. Gaster predicts that Betty will likely attack a highly-populated area like the school or the arena to gather more souls.

Asgore proposes Gaster and Undyne both go to the school to defend it, but he refuses, saying he will remain at the house because Papyrus was unfit for fighting. Unaware of her lacking confidence, Gaster believes Undyne will be more than capable of handling the school without his aid. An explosion then erupts from the city, causing everyone to go to their posts.

While trying to find a way to reverse Sans' state, Frisk and Toriel enter the house with a severely wounded Asgore. Gaster is noticeably concerned for his friend's well-being, before Frisk requests to speak with him privately.

Frisk approaches Gaster about wanting to reactivate an old experiment that will allow the former to enter The Void to fix his "glitching" condition. Gaster agrees on the terms that Frisk donates samples of his blood to him so he can use it to save Sans. Gaster is hesitant in sending Frisk away with low chances of return, but accepts. Gaster wishes Frisk good luck, as he transports him to The Void.

Along with everyone else, Gaster's memories of Frisk are all switched out with Chara after Frisk gives his soul to him and presses the REPLACE button. This sends Chara back to the surface, and erases Frisk and the game itself from existence.

Game Over

Part 1

Asgore and Toriel had found Gaster and Chara unconscious in the lab, both of whom were unable to recall what they were doing before waking up. As Gaster is beginning to discuss how they would deal with Betty and Asriel, he notices the blood vial from the sample he took from Frisk, and rushes to his lab to experiment with it.

Gaster tests Frisk's Determination with Monster magic multiple times, but keeps failing to stabilize the solution. Gaster has the idea to use Undyne's blood from The Nullifier Room. Unfortunately, the resulting solution only supplies a finite amount of Determination and will eventually run out. The injection leads to Sans' body mainly running itself on the temporary Determination, instead of the magic provided to him by Gaster, thus resulting in the Boss Monster link between them being cut off.
GameOverPt1 Gaster1.png

Additionally, rather than Sans painlessly passing on, the Determination inside him will force him to experience every lingering moment of his death. Gaster becomes devastated upon realizing that all he did was make everything worse again, and that he lied to Papyrus for nothing.

Gaster arrives in the room that Jessica and the others are in, seemingly confused by her apparel. Papyrus volunteers to go with Jessica on her way to meet Rave Rutrow, but Gaster forbids him from leaving, causing an argument. Papyrus traps Gaster inside a wall of light blue bones so he will have to listen to him. However, trapping Gaster inside the bones reminds the doctor of his painful experience with Betty and causes a brief panic attack, leading to Gaster injuring his son by slamming him into a wall. Gaster tearfully regrets his actions when he realizes he hurt Papyrus.
GameOverPt1 Gaster2.png

Papyrus tells Gaster that the attack hurt, but not nearly as much as everyone treating him like he is blissfully unaware of the situation. Papyrus tells the older monster that he can do whatever he wants, but he refuses to let him go through his burdens alone, and pleads with him to let him help. Gaster claims he doesn’t deserve Papyrus' help and that all he had done was make things worse through constant mistakes. Papyrus then embraces Gaster, telling him that the only mistake he can make is not asking for help.

Deciding that Papyrus is capable of defending the house without him, Gaster volunteers to accompany Jessica on her way to the city, which the younger skeleton happily accepts.

Part 2

On their way to the city, Gaster and Jessica both struggle to start a conversation. After an awkward moment, Gaster tells her that he has many things that he wants to say, but can't find a way to put them into words. He then tells her that he would like to take a small nap on their way.

Gaster later eavesdrops when Ronan Cass explains Rave and Jessica's history to Undyne. He learns that the City's former leader was Noah Rutrow, Jessica's husband and Rave's older brother.
GameOverPt2 Gaster1.png

Gaster is shown to be concerned about the ground shaking, while patrolling the streets searching for Fear blobs. After there being no traces of blobs on the streets, a creature called "The Kumuzilla" rises from underneath the ground and towers over a horrified Gaster and Jessica.

Upon seeing his Boss Monster soul, Kumuzilla recognizes Gaster as a threat and attempts to kill the frozen monster with a massive tentacle. Jessica grabs Gaster's arm and the two try fleeing to safety, but Gaster is forced to block the attack with his green Chroma hands. As The Kumuzilla heads toward the school to collect more Human souls, Ronan contacts reinforcements to help stop it.

Despite everyone's efforts, no one can manage to cause any substantial damage to the massive blob. Three of the backup troops are killed by smaller blobs dispatched from The Kumuzilla, and Ronan is put in critical condition after taking a lethal attack meant for his son, Hugo. Realizing they stand no chance, Jessica contacts Rave and tells him he is authorized to use whatever he brought with him to help. The Kumuzilla smashes a building and Gaster tries to stop the broken sections of it from crushing him and Jessica, but his Chroma hands eventually give way, and the two are buried under the debris.
GameOverPt2 Gaster2.png

Gaster and Jessica wake up buried deep underneath the rubble, relatively unharmed, but Gaster is pinned under massive rocks. The roof begins to shake, indicating that it will soon collapse on both of them. Jessica reveals that she has one of Alphys' teleporting devices they could use to escape, but a disheartened Gaster tells her the device will only transport one person, and that she should use it to leave him behind.

Refusing to abandon Gaster, Jessica tries to release him from the rock, while Gaster frantically tells her to leave it. Despite his pleas, Jessica stubbornly persists in saving him, even going as far as cracking her already damaged soul when trying to use her gun. Despite not being fully ready for it, Gaster tells Jessica that he forgives her for everything she's done in an attempt to get her to save herself.

These words have the unintended effect of restoring Jessica's lost Integrity. She instead activates and gives him the device, telling a shocked Gaster to make Betty suffer. Jessica soon dies after his departure.

Finding himself alone inside Rave's lab, Gaster weeps silently with the realization that yet another person perished because of him. He raises his head with a new resolve to not let the former leader's sacrifice be in vain, and to get his revenge against Betty once and for all.
GameOverPt2 Gaster3.png


Rave discovers Gaster soon after he is teleported to his lab and recognizes him from a chapter of a seemingly Monster-related novel. Gaster implies Jessica's death to Rave by telling him that he's been promoted to city leader. Gaster then tells Rave he will assist the people in the arena so Rave can prioritize dealing with The Kumuzilla. Noticing Gaster's broken leg from being trapped under the rock, Rave heals him with an Arnicite device that fixes the bones and injuries. Physically healed, Gaster goes to leave before Rave stops him and asks how he'll manage to take down the massive blob.
Hate Gaster.png

Gaster glances back and sees a younger and happier version of himself in Rave. He then tells the Human scientist that he looks smart and can figure it out. With these final words, Gaster goes to confront Betty, leaving a confused Rave alone.


Arriving at the arena moments before Toriel can be killed, Gaster saves her by cutting off Betty's arm. Knowing she can't defeat Gaster as she is now, Betty flees. Gaster looks over to see a severely wounded Asgore lying on the ground. Concerned for his friend, but focused on the task at hand, Gaster proceeds to pursue Betty. Toriel asks Gaster where he's going. He tells her she can do more for Asgore than he can and also asks Toriel to at least pretend she cares for monsters this one time.
Animosity Gaster1.png

Papyrus and Sans arrive at the scene to assist in defeating Betty. Betty arrogantly challenges them before Gaster arrives and punches her away. Upon seeing Sans, Gaster is briefly saddened before the skeleton family shares a short moment. Betty interrupts them and says although they have her trapped in a chain, it's "only as strong as the weakest link". She then rushes to attack Papyrus, but fails when the young skeleton launches her away with a bone. The three monsters prove to be too much for her to handle, and HATE slowly gains dominance over her with her magic running low.
Animosity Gaster2.png

Betty eventually grabs Papyrus in a massive fist and starts to crush him in an attempt to keep the other two back, but Sans appears behind her and blasts her away. Gaster begins healing a wounded Papyrus. Seeing his brother injured, Sans rises in the air and summons a massive quantity of Gaster Blasters with his Gaster Blastermination.

Realizing what will happen next, Gaster calls out to Sans to stop, as Betty uses Rhabdophobia, turning the blasters against him. Refusing to lose his son again, Gaster uses his Duality hands to protect Sans from the blasters.

Soon after the blasting stops, the hands break and Gaster falls unconscious. As Papyrus rushes towards him, Bete aims Sans' attack at the two. Just as Papyrus is about to defend, Sans teleports in front of him, summoning a second Blastermination attack. The two forces clash, as Sans begins to melt from the Determination. He successfully counters Bete and sends her into a building. Sans then turns to dust in front of his family, and his soul shatters.
Animosity Gaster3.png

Papyrus collapses to his knees and begins to cry, as Gaster begins to remember all of his efforts to save Sans, and how it was all pointless in the end. Gaster then snaps entirely, just as Bete launches an explosive projectile at Papyrus. Shielding him with a Kindness Chroma hand, Gaster proceeds to subconsciously reverse the link between himself and his son, sending the magic formerly flowing into Papyrus back into himself. Gaster then challenges Bete, prompting her to attack him, as he quickly begins to counter all of her assaults.

Gaster, seemingly expecting more from Bete, observes her weakened state, and prepares to activate his ultimate attack: Polychromatism. With a roar, he summons a massive Gaster Blaster, two Duality hands, and seven small hands. He quickly rips Bete’s legs off and starts to vaporize her with Determination beams. However, before Gaster is able to finish her corpse completely, Papyrus selflessly cries out to him when he feels his father’s soul begin to crack. Gaster, realizing that continuing would drain his son of too much magic to survive, drops the beams and leaves Bete's body as a husk.
Gaster Animosity Polychromatism.gif

The link then returns to normal, and part of Gaster's magic once again begins to flow into Papyrus. Gaster then falls unconscious, and Papyrus catches him as he drops to the ground. However, soon after noticing the remains of Bete crumbling away, Papyrus comments that he feels something is wrong, and attempts to leave.

Due to not being entirely vaporized, Bete's corpse is consumed by HATE. As the being awakens, it creates a dome that casts an illusion on Papyrus, making him think that Gaster has died in his arms. Papyrus, paralyzed in both grief and fear, can’t move as HATE raises a blade to kill him. However, Chara is able to jump in the way and take the blow. Asriel arrives behind him, as Papyrus notices Gaster still alive in his arms. Chara then challenges HATE to a final battle in the city.


Gaster is seen still unconscious from the events of Animosity. His body is taken to safety by Papyrus and Asriel before Chara and HATE start to fight.

In the aftermath, Gaster awakens in a bed. Sitting upwards, he watches a resting Papyrus, who also quickly awakens and notices Gaster conscious. As Papyrus states that he now feels far more energized than before, Gaster immediately apologizes for his past actions, stating that he had hurt his son, despite having the responsibility of protecting him. Papyrus, however, dismisses the apology, stating that many issues arose due to his incompetence involving his own lack of violent intent. He explains that, if he had been more willing to inflict harm upon his enemies, Sans could’ve lived longer.
Hope Gaster 1.png
As Gaster listens to Papyrus’ words, he experiences a memory from his past, regarding an incident in which he had once attempted to utilize violence to solve his problems. Accepting his responsibility as a father, Gaster speaks to Papyrus, stating that everything he had done had only ensured the safety and wellbeing of others, adding that his kindness had allowed Sans a final opportunity to see their family together. Gaster continues by explaining that, although Papyrus does not possess exceptional power, his true strength derives from his voice of reason, and that he would always be present to assist his friends and family whenever necessary.
Hope Gaster 2.png

He adds that Papyrus has been the sole reason that Gaster had managed to escape his darkness. Gaster concludes by stating that he’s proud of who Papyrus has become, requesting for his son to never change his ways. Papyrus, overwhelmed by emotion, subsequently rushes to tearfully hug Gaster, who easily accepts.

Gaster is later seen alone in a room, suffering from mental instability. As he looks up towards the room’s mirror, a monstrous figure begins to form behind him. It clutches his shoulders, as the mirror begins to crack. Then, it is revealed to be an un-composed creature resembling Gaster.


  • Gaster was the Royal Scientist of the Monsters and Humans.
  • Gaster is the only known Monster to have both Chroma magic and blaster magic.
  • Gaster becomes fatigued when his Chroma hands are forcibly broken. This is because he puts considerable concentration into them, and significant magic is taken away if he doesn’t manually disperse them.
  • Gaster’s purple Chroma is gone due to a tragic event in the past.
    • The Reason he is able to use it in Animosity is due to him draining Papyrus' soul of magic to temporarily restore it. However, once he re-established the Boss Monster link with Papyrus, he loses access to it again.
  • Some of Gaster’s abilities, such as the Void substance and the unnatural purple Chroma, are abilities he obtained through his existence in The Void. However, Gaster no longer possesses these capabilities following his return in Your Best Friend. He can, however, still block game buttons.
    • Despite the similar appearance, the Void substance is not actually HATE.
    • The unnatural purple Chroma, that was capable of duplicating Sans' attacks, is much different from his normal purple Chroma. As shown in Animosity, his actual purple Chroma is capable of making purple spikes that slow healing magic.
  • Because a large amount of Gaster's memories were suppressed after his experience in The Void, he doesn’t recognize the illusion of Agate when she drops Betty off at his house in Dust.
  • If he was aware of Betty's ability to use Rhabdophobia, it's unlikely he would have lost in his first fight with her.
  • When Gaster's magic is stolen by Betty in Do or Die, the reason he couldn't summon anything more was because Betty was still using his own magic to supply it.
  • Gaster would have likely forgiven Jessica at some point, but he wasn't ready when he said it to her near the end of Game Over Part 2.
  • Excluding the nap in Game Over, and the time he spent unconscious, Gaster hasn't slept once throughout Season 2.
  • Gaster could have still defeated Betty without draining Papyrus' soul, but he was so outraged by Sans’ death, that he wasn't thinking of the side-effects.