Etienne

Etienne appears in Interlude, a four-part Mage backup series in Grendel.
 
Etienne meets Marie, a French girl, in a rural sculpture park.  He seduces her, then jumps into the nearby pool.  He emerges as a black, demonic-looking horse, and attacks her.  However, Kevin Matchstick arrives and defeats Etienne, saving the girl.