The non cannon backstory of bill cipher! apart of the "Cold hearted hero." series (thats the name until i think of a better one.) The series is non cannon/cannon backstories of villains. its meant to make you sympathise with them and help you understand how they became who they are.
short version: William Pines is a... special kid. he somehow has chicks wishing they could date him yet is oblivious to that. He can be a bit of a nerd and he isn't scared of anything. well except Alcor. Alcor Cipher is the demon of gravity falls. A chaotic one at that. he makes deals and ultimately screws everyone over. After a moment with his sister she runs off. the next thing he knows weirdmaggedon is unleashed with Alcor as the leader. One thing leads to another and there is only one human left in gravity falls. the rest dead or stone. Mabel, Stan, Ford, Wendy and Soos are dead. William himself is captive, kept in chains on the floor of the throne room. when Alcor comes in however its with a potion. and after forcing William to drink the potion the timeline is killed. without its protagonist the world changes to fit its new hero and villain. that dosent mean the villain wanted their role though. the picture fills in what the potion dose. and in case you still dont know a short version of William is Bill. And a star in the big dipper constellation is known as Alcor. Thanks @Akystaracer22 for the story!