Causal Nexus -

“The causal nexus divided when Nyssa changed history... causing the universe to exist in two quantum states and releasing blinovitch energy.” Tardis | Fandom

“Wally learns the hard way that good intentions don't off set the consequence of time travel... Wally's actions have already set off a chain of events that can't be stopped.” Fanfiction.net

For years, Elias had been haunted by a memory: a silver-haired man giving him this very notebook when he was just a boy. "The world ends in fire," the man had whispered. "Unless you build the Machine."

In a panic, Elias realized the "fire" the man spoke of was the very act of building the machine. He grabbed the notebook and stepped through the shimmering portal.