Sigil, City of Doors...
Guant and kind of skeletal, Lothar is a powerful mage who likes to “collect” things. He is likely some kind of necromancer, and employs hard-to-kill but relatively not-powerful servants.
You probably shouldn’t ask him about his past. Likely not a good idea. However, if you are interested in the history of Tubatron, you could probably ask Ooze. I’m sure he’ll have something to say.