Collect 3 Lion Rings, via the Lion Ring Quest, and say Lion Rings, then yes to Mordenthal, located in his temple, in the Mountains North of Stonecrest.
Note: You must be of evil alignment to perform this quest!
Rewards:
In total, 1 reward will cost you 1125 Moon Tug Scalps (i.e., 375 Moon Tug Scalps per Lion Ring)!
You can repeat this quest at will.