Undeterred's page

Well, the only real issue I see here is the mechanic that you want to add. It definitely has the right feel to it, but I would suggest a change to it.

Instead of it giving the debuff to AC on the target every attack, make it to where that effect only applies on a Full Attack. It would really give it the feel of keeping it pressed against the target instead of just swinging it at the target every couple of seconds.

So, basically, someone would do like 2 attacks as a Full Round Action thingy (sorry I'm not entirely familiar with all the terms yet), and with each successful hit from those attacks would apply the AC debuff.

[Ex: You hit against the targets 17 AC on the first attack of the Full Attack, then the next attack would only require a 16 to hit.]

Doesn't look like you are. I might be wrong here, but I'm pretty sure you didn't "allow" your ally to kill the target. It was more like an accident. That being said, you could probably still roleplay a little bit of guilt or anger or something along those lines.