LostSoul
Adventurer
So in other words it would be like you having a 15% chance to auto-kill a monster in the first round of combat... but even if you don't you have the same chance to battle the monster on the same terms as everyone else... in other words it's not an 85% chance to fail... it's a 15% chance to auto-succeed and then a regular chance to try and succeed.
I think it would be more like saying the Fighter has a 15% chance to hit AC 0... but if, instead of rolling the dice he describes his attack routine and lets the DM adjudicate the results, he has the same chance as anyone else.