According to him, he is "immune to the plot", "can transcend time and space", and kills anyone when he feels like it. He has his own team of monsters who are probably his friends. According to the developer commentary and the newspaper
The Beaver holds, Flumpty kidnaps
the player because he feels like it, and he wants a friend. If he catches the player, he will kill them, resulting in a jumpscare and not becoming friends, and instead killing them and eating their eyes. If they survive, the player and Flumpty become best friends. Flumpty himself appeared before the beginning of time, being the chaos god of death. He has more than one victim, and as we know, he staged one apocalypse.