I was running around the Deadlands and Necrohol Nabidis killing mobs in a xp/farming/exploring run awhen I accidentally popped Deathscythe. He thought spamming annuls would be fun and annulled my whitemage right as decoy wore, that led to a a 5/6 without mp situation, so I zoned him and run back to check if he would still be up. I melee a skeleton to start to get some mp back and end up popping this guy (taken from lolgamefaqs):
Rare Monster No. 38/80
Name : Helvinek (367)
Drops : Grand Armor, Grimoire Togail
Steal : Magic Lamp
Original : Darkmare
Rare Rank : **
Location : Necrohol of Nabudis
Appearance : Appear after you have killed six Over Soul in second section from Salikawood. If you didn't find six Over Souls, just defeat the other enemies as many as you can, you will eventually get to find six Over Souls.
Best thing about him is I guess he can pop in multiple zones. Since I couldn't shake him (he fallowed me through 3 zones, popping next to me as my screen loaded up), he took down my no-mp party members out one by one as I was trying to get away from him. He also, like other mares, warps within striking distance when he wants to hit you.