The Headless Horseman is an epic x2 mob that spawns during the Nights of the Dead festival from a dead looking tree in Neklutos Forest near the Darklight Woods entrance. He drops a couple of awesome pieces and is an easy kill if done right.
I managed to put together slightly over one and half groups for him. To get him to spawn, at least one member of the raid force needs the necklace obtained from doing the Halloween maze. He’s on an one to three hour spawn timer, and upon spawning, goes for the person with the necklace in their inventory in an attempt to snatch it off. If the person dies, the necklace is consumed. Otherwise, it can be used again for subsequent spawns.
In only place where The Headless Horseman can be killed effectively is on the grounds with the field of bones near the tree. My first attempt lasted almost 45 minutes before wiping because we were clueless on the strategy and tanked him elsewhere, where he had a 99% damage resist debuff. Stupid of us, but we were all once young and naive.
Tanked in the right spot, he was easier than cake and took little effort.