ToME: the Tales of Maj'Eyal

Talent mastery: -0,20 Cunning/Stealth should be in RED colour or change for positive bonus. Now it is very useless.

PizzaPL

I'm pretty sure it's intended to be negative. The description mentions the screaming mouths that it's made out of, so apparently it's making noises while you're wearing it -- hence the stealth penalty.

Indeed, though it should perhaps show up in red. I certainly don't think it makes the item useless - just less useful for rogues. It's one of my favourite early game arties actually.