Yeah. From the Nightmare Realm. [ No really, a literal nightmare, Hiro. ] Bill basically wanted to be in our world to throw a party. The Nightmare Realm isn't on a physical plane so he couldn't directly affect our world unless he was able to enter it directly. That's why anytime he wanted to get something done, he had to possess someone. But with the rift, he could actually bridge the gap between our world and his and...well, you get the idea.

[ His tone dampens a bit. ] That might sound harmless enough, but Bill's idea of a party was sort of...detrimental to all of humanity. He started the Weirdmageddon.