Imagine the timeline as a path with different possibilities generating alternate realities, such is the background of the TriVerse.
In the TriVerse, three possible alternate realities form three different realms converged and connected by the Nexus Gateway, where beings from each realm can travel to the other three realms.
Never stable and always fighting to be the only realm, each realm has a Sentience represented by the collective beings in their respective realms. It is said that one day, when one of these Sentience grow strong enough, they will merge the weaker realms into one unified plane of existence.
Who wins, who loses, which realm triumph depends on you.