This is to resolve a dispute that came up in a recent match.

I had Eddard Start in play with Winterfell Castle so he had a total of 4 Strength. My opponent attached Stinking Drunk to him bringing his strength down to zero. I had Eddard participate in a challenge with another character (forgot the specifics of who) and the chalenge was won. It didn't make sense to my opponent that Eddard would be able to claim power from Renown since he didn't contribute to the challenge. But my understanding is that there is nothing preventing a characer with zero power from participating in a challenge and getting the effect of keywords like Renown as long as at least one other character is involoved to allow the challenge to be won. Thoughts?

You were right. Characters may participate in a challenge even if they have 0 STR. They will still give you some bonuses for participating (Stealth, Renown, Deadly, abilities) so having them in the challenge will not be useless. In fact, including them might even lead you to victory.

Take a look at Former Champion. After getting some power he gains Stealth, Deadly and a couple of icons at the cost of being a 0 STR character. Your friend might think "What a useless character!" but he's quite good, even though he isn't able to win you challenges by himself.