Yeah, we had that issue with Rokugan and Oriental Adventures and the shadow taint.I immediatelly had flashback to 3.5 taint. You do not want anyone to see your taint, as you never know how people may react to being shown your taint, so you may waynt to conceal your taint....
I forgot about the ASI increase....hmmmmm.5E has so few feat slots that I generally thinks it's a good idea to give extra feats for free at levels: 2,5,9,13,17,20
maybe remove +1 ASI from them if that would make PCs too strong.
So if a PC had a 12 Con, they could get 6 free feats and start showing changes, with a total of 12 before becoming and NPC?Feats would give corruption equal to their level.
If corruption equals half your Constitution or Charisma score, it is visible physically or mentally respectively.
If corruption equals 75% your Constitution or Charisma score, it is very restrictive physically or mentally respectively and causes heavy mutation or san loss.
If it exceeds either score, you PC mutates to an unplayable mass.
Its harsher.So if a PC had a 12 Con, they could get 6 free feats and start showing changes, with a total of 12 before becoming and NPC?
That much power would be tempting indeed. Seems a bit high. My players would gladly take 5 free feats and say "thanks", never gaining another one.

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.