dipper can run as much as he'd like, but he can't hide – not from the nightmares that will catch up to him regardless of how much he may attempt to delay sleep. all those years ago, ford did the same in his desperate attempts to avoid being possessed – it's funny how the "smart" pines twins ("smart" and "pines" being paradoxical, really) can be so stupid.
and so, upon dipper falling asleep, just like every night he failed to avoid sleep in the months before, bill is there. not physically yet, no, instead, he offers a scene he's been waiting for –
a sky set ablaze, creatures with their flesh turned inside out howling unnatural noises, humans with shuffled features frozen in terror... the chaos he's been prophesied to bring for a billion years, and he will, even if it means millennia more of trying.
peer a little closer, and the star of the nightmare will realize the figures surrounding him are all friends:
his sister, melted in a frozen puddle, dozens of eyes scattered throughout her malformed statue, dripping with tears as four hands reach towards dipper.
his uncles, twin faces melded together in frozen terror, with a misshaped crown of six severed fingers.
then his parents, wendy, nearly every resident of gravity falls (among the few friends he held back home), each D̴̡̫̜͊I̴͚̊͒̎̈́͠S̵̡̺͖̓͑͝͝T̴̥̃̄͒͌̿Ö̵̖́́́̃R̴̜̳̣̈́͌͐T̵̨̤̮̫́Ę̵̘̹̭̯̾̔̀͐D̶̺̓̆ yet undoubtedly, them.
and after dipper has a long moment to reunite with his friends and family, bill appears behind him – this time, in the human figure he's been forced to inhabit in evermore, sitting upon another statue: one of dipper himself, but with too many limbs and a face devoid of any features, bleeding eyes and screaming lips and burning nose spilt on the flaming ground beside him.