Definitely not steam-punk. He's a suave gentleman wearing a mechanical stasis suit with spider-legs.
It's kinda like...Dungeon Punk.
This guy would be one of those typical geniuses you get in early 20th century or late 19th century settings, that one older gentleman who drinks in knowledge, a scientist of the older years who is proficient in biology, chemistry and physics.
The stuff he makes is like science mixed with magic, with the rules of science dominating it. Strange rituals of circles and polygons, each degree carefully calculated and each rune put exactly in it's right place. Sleek and silver contraptions that have magic running through their wires instead of electricity. Ritual magic
in essence but so much more, he's a fantastic scientist.
Suffice to say, he's rather unique in a world where most powerful magic users are simply born with X powers and only spend about Y amount of intelligence into learning how to shape and use it. He was born with Y amount of power and spent 3X intelligence into learning how to use it and every other magic he was interested in.
For example, Marvin knows a lot about using runes, which is sort of the algebra of the science/magic world. One rune creates fire, one rune creates ice, one rune powers them up and then you mix and match them all. It's not anywhere near as sciency though so Xenon looks down on it a little as too common. Preferring to learn arts where his huge type
of intelligence gives him an edge.