An idea I've been fiddling with for awhile, a central antagonist for Adrian's story/setting. One of the mythological Great Princes of Hell as described by Ars Goetia.

"A Great Prince of Hell, commands twenty-six legions of demons. He teaches astronomy and is knowledgeable about herbs, plants, and precious stones."

In this version, he also had a hand in creation of alchemy, and it's subsequent introduction to mortals. While he rarely interacts with the mortal realm, he certainly has some not-so-benevolent plans for it, as the inventions and artifacts he left scattered through the realm have created more trouble than any benefits. Charming, polite and considers revenge and grudges to be beneath him, a waste of time and resources. Takes any losses with dignity and in stride, going back to the drawing board whenever his plan gets thwarted, or somehow manages to turn said loss into a benefit for himself. Considers the Order of the Burning Shield to be worthy adversaries, and despite being on opposite sides he enjoys meeting up with the Order's current leader, madame Ellena Ainsworth, even if she doesn't really reciprocate his enthusiasm. While normally calm, polite and casual with others, he emanates an aura of patronizing superiority. Can be quite affectionate and fatherly towards those he takes up as his apprentices. That said, however, he sees everyone as having their part to play in the grand scheme of things; if their survival is beneficial to his goals, he will ensure they survive. If they have to be sacrificed, well then...unfortunate, but it must be done.