Fel Reaver

The Fel Reaver is a level 70 elite fel reaver that can be found patrolling around Hellfire Peninsula.

While questing in Hellfire Peninsula, it's quite common to have one of these giant engines of destruction sneak up behind you. If your screen starts shaking and you hear a noise somewhere between a steam engine and a roaring beast, find shelter! These towering behemoths, luckily, have a small aggro radius for a Lv. 70 elite.

Tactics
A Fel Reaver can be downed by a three man level 70 party composed of a tank, a healer, and a DPSer - however with proper gear and/or a pet, it's soloable and has been soloed without NPC help as far as at least January 2008.

While it does take a while, the damage output of a Fel Reaver is comparable to that of any random 70 elite and completely focused on the tank (in other words, surprisingly low for something of this size). As of version 2.1.0, stealthed rogues and druids within the ground-shaking range of the Reaver, even if outside aggro range, lose stealth, seemingly with each shake/roar.

To obtain the Key for Shattered Halls, you must kill a Fel Reaver and forge the key in its fiery carcass. YOU DO NOT HAVE TO LOOT ANY QUEST ITEM FROM ITS CORPSE. Just use the quest item [Unfired Key Mold] at its corpse (no matter who killed it).

A Fel Reaver may also be pulled while just northeast of Thrallmar. If kited to the wrecked caravan just outside of Thrallmar, after which the player drops aggro through a skill such as Ice Block or Feign Death, the guards will pick up aggro on the Fel Reaver, and eventually kill it, allowing you to solo this quest with relative ease.

Trivia

 * When The Burning Crusade was first launched, many people questing in Hellfire Peninsula fell before this fearsome beast, despite the earthquake and horn that heralded its arrival. With the advent of Wrath of the Lich King, it is not uncommon to find the Fel Reaver dead, having been slaughtered by a level 80 player seeking a little payback.