Hoi bub, i think you forget a key piece of lore about me. I'm invinsible as an SCP object. determination or not i have my own powers: telepathy, manipulation, corrosive acid that can kill anything, and brain death when someone places mask on their face, that is any living thing. Undead things and corpses are different. Thus, Gaster could be manipulated into placing me on his face, disintegrated with acid, or just willing him to m*urder himself somehow