I was thinking of game names again.
Sanctum is taken. Soulmancer is taken. Soulmancer's Sanctum of Souls is too long, though it does have three S's which can help for an aesthetically pleasing cover. Sanctum of Souls isn't taken but it was something within Final Fantasy XIV, it also abbreviates to SoS, which is nice.
Return of the Soulmancer could work as most characters found in the game express their surprise and joy and seeing a soulmancer once again.
Soulmancer Incremental or Incremental Soulmancer could also work, but it puts a literal limitation on the game and could put off potential future players who make an assumption based on the name alone. Also it's a bit stale.
You could always keep the name TBD which allows for the game to take any direction you want in the future. You could come up with a million acronyms for it.
The Battle Dimension
These Buildings of Death
Thick Butts, Damn!