Well go to Argent Vanguard, in Icecrown, and use the Siege Towers.
Can any of you all believe this joke Blizzard put in, by having the Reckoning Bomb in the game as a special attack for a Siege Tower?
Anyway, the quest is very interesting. So destroy 100 Undead, and as you build up power, you can then Unleash your most powerful attack (The Reckoning Bomb )
I had to fight one horde over a tower, but that was nothing.
I did die after the quest, cause one of those stupid Elite Dragons one shotted me, as I was getting off the Siege Tower. > :-\ :'(
But lease we Get to use Flying Mounts as a ghost, running back to body. :-*