Definitely.
Since Phase first remembers, he has been exposed to the broader multiverse. Because of the dream-like nature of his existence, reality warps around him, and he will often stumble from one world into another. Despite this, he hasn’t yet run into any of the characters from the Myriad RP yet, so the way I imagine introducing him into the RP is to have him exploring somewhere, and he opens a door that leads him into another world right where another character is randomly at.
Alright, sounds like you’re good to jump into this war, then!