Fel reavers are enormous demonic machines found in Outland. They are immensely powerful foes and are constantly emitting fel green smoke.
Fel reavers cover ground with incredible speed, due to their long legs and an internal power core that is "powered by a scalding core of fel fire" that "burns much hotter than normal fire",[1] and not nether gas.[2] They also seem to have a Heart of some kind that 'beats'.[3]
It is said that the cunning mo'argengineers of the Burning Legion pushed their gan'arg workers for weeks in the construction of the first fel reaver, a massive construct that could easily raze fortified towers or tear the wings off an airborne gryphon. The forge camps then began to mass-produce these fel reavers to smash the mortal forces of Outland.[4]
Currently not much else is known about the Reavers' construction or origin. The Burning Legion uses them as sentinels all around Hellfire Peninsula, including around their forges to the north (Rage and Mageddon) to oversee the work on their cannons. Much of what is known about fel reavers comes from observing the ones in Hellfire Peninsula.
Two locations in Hellfire Peninsula are based around ruined fel reavers. Reaver's Fall, in eastern Hellfire Peninsula, is the location of remains of a destroyed fel reaver, with a handful of trolls, orcs, and tauren cheering and dancing around the fel debris. At this area, players can execute bombing runs against the legion front. Another area, Expedition Point, is near the gateways of the Legion. It is also built around fel reaver parts that are being forever hacked away at to bring to Stormwind City in order to be melted down and remade as weapons to use against the Legion.
Fel Reavers can dance. The dance animation can currently be seen in-game used by the XT-002 Deconstructor, which shares a wireframe with the Fel Reaver, before engaging.
Clockwork giants also share the wireframe of fel reavers. It is possible this is more than a modeling shortcut, as it would not be the first connection the titans have to the Legion.