Quote Originally Posted by Segev View Post
Assuming (as I forget) arcane fusion is natively 5th level, making it a Sanctum Spell would cause it to count as 4th level when cast outside the designated Sanctum. But that also makes it take a full-round action to cast for modifying it with a metamagic feat, unless that Arcane Mantle thing fixes that.
To most people, including myself, Sanctum Spell changes the effective level only, it doesn't change the spell slot.

A sanctum spell uses a spell slot of the spell's normal level.
As for the full-round action thing, I believe that Arcane Spellsurge should cover it.