I'm running a high-level Norse-themed adventure with Odin and Thor running around messing up giants.
The Odin-wizard used true polymorph to create a human from an oak log (see the saga), and he wanted it to be the CR9 Champion from Volo's Guide to Monsters (p. 212).
I let him do it because it was cool. I have in my head, however, that the rules only allow an average example of the race - like a human commoner, not a champion, but I can't find the rule or ruling that makes me think that.
Is creating a CR9 human champion a RAW/RAI use of true polymorph?