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

He didn't have a choice. To ensure he grew up to build the machine that would bring him here, he had to give the boy the book. He had to be the spark that started the fire. Causal Nexus

“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 “The causal nexus divided when Nyssa changed history

Elias stood in the ruins of the Great Library, clutching a charred leather notebook. He was a "Time-Sensitive," capable of feeling the hum of a —a point where time tracks diverged and collided. He had to be the spark that started the fire

The concept is widely explored in fiction and philosophy as a way to understand our interconnected reality.

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.