The card text says:
While attached character is participating in a challenge, all other characters lose stealth, renown, and deadly.
Lets say this is attached to my character, who has stealth and is currently an attacker in a challenge. Now lets also say my opponent has 1 character with stealth from two sources.
Will that opponent's character lose both "instances" of stealth or just 1 since the Chariot doesn't specify a number for how many are lost?