Yuan-Ti Half Blood
This creature appears somewhat human, except for a few tell-tale serpentine features, like the off-colored skin and the obviously snake-like eyes, as well as the patches of scales on their skin. If it weren't for the fact that she was surrounded by creatures very much like her, it would be hard to pick her out in a crowd of humans, were she properly clothed. Her scimitar has small drips of acid sliding off of the blade, and she flicks them towards the ground as she runs towards you to the attack. 
A Yuan-ti Pureblood looks less obviously snakelike than her kin, but due to her company, is still recognizable as less than human. She has a handful of darts, and she ducsks in and out and around the ruins of her home, taking opprtunistic shots at you with the heavy, fang-like darts. When the darts hit you, or clatter to the ground, you see a thick green liquid ooze out of them. 
This Halfblood is very obviously possessed of strong arcane talent, as shown by the spells and defenses already woven around her. She seems to eschew protecting her allies infavor of making more immediate arcane attacks directly upon you and your allies. 
 Staff written creature descriptions by Tormak.