I've been going through a daily exercise of creating and posting monsters for Tunnels & Trolls and giving them a unique ability or perk, to keep them from just being sacks of damage taken and damage given. I've enjoyed it so far, because even though monsters in T&T can be played very simply, the extra tweak makes them more exciting to me. I look forward to using them as a GM in a T&T game session.
I'm pondering if the same could work with OSR / D&D Heritage monsters.
Something along the lines of:
"If the Orc's hit scores maximum damage, he pulls his target in for a bite on the face. If the target is not wearing a helm, roll against unarmored AC, inflicting 1d3 damage on a successful hit."
"If the Troll hit's with both claws, the Troll's bite automatically hits for maximum damage".
"If the Goblin hit with a natural 20, in addition to normal damage he wraps himself around the PC's leg. PC must save vs Paralyzation or trip and fall prone. If save is successful, next attack against the goblin holding on to the leg in question is at + 2, as he is fairly immobile."
Maybe I'm over thinking this stuff. It certainly wouldn't have to be done for every creature in the books, or even apply to every creature of the type it is written for.
In any case, if you were inclined to add a "twist" to your PCs run of the mill adversaries, what kinds of twists would you use