Eris has multiple powers including Knife summoning, Bones, Gaster Blasters, Daggers, teleporting, etc. From sans
Sans has no true hate against frisk knowing she was controlled to kill him multiple times but he has nightmares of it, he is extremely protective over Eris
He claims he has no feelings for killing all of the monsters including his brother
Frisk is usally kept quiet to herself but will open up to her daughter or Sans
Gaster is sans father who fell into his creation
Arial is sans mom