Mage Creed is a silver chest drop from Co-op Quests.
|Unlock Gunslinger or Mystic||5|
|Forge Class Champion Weapons||10|
|Rebuild Class Champion Weapons||25|
While there is a possibility of it dropping from any stages, the rate is low enough to not ever expect one to drop outside of extra stages. Most players farm Corridor of Puzzles or Lost in the Dark for their relative easiness when collecting Mage Creeds.