Marvel multivers
The Loki tv show explain a lot about the multiverse and I made this video to schematize his history.
In the beginning, severals versions of Nathaniel Richards of different timelines fought themselves to dominate the multiverse, until one of them used Alioth to destroy the opposing timelines.
He allowed several timelines to exist and grouped them under the name of the «Sacred Timeline». He created TVA to intervene at each nexus and prevent them from multiplying.
After Sylvie killed him, the timelines multiplied again without any supervision, creating a new multiverse.