"It is good to see you again Sans."
Sentinaltale Gaster to Sans
Gaster is one of the main characters in Sentinaltale. He lives in the White Void after having fallen into the Core. Scattered across space and time, he is trapped in the void and cannot leave. He rescued Frisk from Chara, in hopes that she would help him put a stop to the slaughter.
Due to the magic of the White Void and being torn apart, Gaster has an unstable form at best. At worst he will turn into a black puddle with hands and a head. He has a scar above his right eye socket and one below his left eye socket that trails to his mouth. Each scar is the result, according to him, of "failures." He also has holes in his hands that he also attributes to failed experiments.
He is a bit overprotective of his brothers, he feels some guilt about what happened in the Core as well as some guilt that he could not be a better brother to both Sans and Papyrus. He is often rather eloquent and polite, as he is used to using court mannerism; his exile into the void hasn't changed that. He was a workaholic when he was still alive in the timelines.
He can see the soul of a being without trying. He can also see and read Code, but he cannot manipulate or change it. In combat he can summon Gaster Blasters, bone patterns and six bone hands that each control a different type of magic attributed to six of seven known human souls. He often summons one or more of his "hands" to communicate through sign language to others as he is incapable of speaking English and most do not understand Wingdings.
He feels guilty that he wasn't a better brother to him and Papyrus, but cares deeply for his brothers. He also trusts Sans' judgement on many things, even though he is the older brother it sometimes seems like Sans is actually the older one.
She is a good friend. He saved her from being killed by Chara, hoping that she would be able to help him put a stop to Chara's rampage across the timelines.
He despises Chara for all of the killing that he has done and the damage against innocent lives.
He knows more than he is saying about her, but to keep good faith he does not speak about what he knows and she seems to appreciate this.
Gaster sees him as just another brother, even if they are not actually related. He finds Inky both fascinating and amusing.