All three games are not meant to be directly related to one another but rather exist in tandem.

The Sea Of Quanta is a very important place in the world of Honkai Impact 3rd. It is the place where bubble universes reside (A multiverse) and where several characters were sealed. The Sea Of Quanta is where Quantum Shadows are born and produced.

honkai impact 3rd, genshin, and honkai: star rail all take place on the same larger "imaginary tree" that is the universe, although their world "leaves" are different. the traveler and the unknown god (the heavenly principles) are from a honkai impact 3rd leaf.

Imaginary Tree (Theory) This theory describes the various worlds existing in different spacetimes as having a tree-like structure. Every branch is a specific path along which worlds might exist, with every leaf being the marks these worlds have made along the parameter of time.