Tanking the Blue (Another Blue Mage Idea)
So what if instead of learning monster abilities, this Blue Mage is able to shapeshift but not into animals or monsters but long forgotten primals whose worshippers are few or no more. In order for them to transform into these beings without the need of prayers is that they make contracts with these beings while the Blue Mage's body acts as a siphon gathering aether around them especially from living creatures to allow them to give these primals shape. They are called Blue Mages for the blue aura that surrounds them when they siphon aether. I got this idea from playing Palace of the Dead where you can transform into succubus and the manticore. Here is the Blue Mage. Could this be a possibility?