I think it’s good world building. High skilled positions like wizards come at a premium. 1000 slaves is probably still cheaper the. One “magically roided muscle wizard”. I think it’s more interesting to think about how a system like this could exist. Slavery is entrenched in the culture which is...
I think that might be a clue as to who he is. He might be immortal, so unchanging face, but his body toughened and beefed up from being through trials and tribulations for a VERY long time.