Oh,oh, let me guess: He/she is reptilian since they don't show facial emotions like other mammals, right? Perfect for an assassin, right? You know, that ice-cold stare no matter the situation or moral implication?
Ergo, Lizardmen do not show emotions, therefore they look like "cool" assassins. Also, i bet that the player can make the assassin to "feel" or even feel regret to better herself/himself.
I hope that i am wrong, i really do.