Zhai Zhu
What kind of thousand year old man is he? is the "pervert/rapey" kind, the "kill before you think" kind, the "encyclopedia" kind, "that one cool teacher in school" kind or the "no matter how much the mc powers up i'll keep reminding him that his still the lowest in the food chain compared to the geniuses of my time (while being secretly impressed by his perseverance/hidden talent) kind"