The Devourer of Souls
The Devourer of Souls is the second and final boss in Forge of Souls. Like Bronjahm, the Devourer is identical in both normal and heroic modes. However, the damage done in heroic is significantly higher than in normal, and healers will have to be prepared for large spike damage.
The most common ability that the Devourer uses is called Phantom Blast. It has a two second cast time, and does a fairly high amount of damage on the tank (about 12,000 on normal, and 18,000 on heroic.) This ability should be interrupted by DPS and the tank whenever possible to mitigate the damage.
It is most important for the tank, and DPS, to look out for an ability called Mirrored Soul, which will be announced with a warning: "Devourer of Souls begins to cast Mirrored Soul!". This ability will be targeted on a random player, and will channel all the damage that the Devourer of Souls receives to the player. This can be a quick death for a party member, so when the debuff is cast, it is essential that players stop all DPS until the debuff ends.
The next major ability that the Devourer of Souls uses is Unleash Souls. This will summon a large number of non-targetable blue ghosts into the room. These will attack targets at whim, and do a minor amount of damage, but can pushback spells as well.
Next on the Devourer's ability list is Well of Souls. The Devourer will leap to a target, creating a large black puddle on the ground. This pool will damage players every second they stand in it, so it's important for players to move out of this if they end up in it.
The final, and yet another highly deadly spell that the Devourer uses is Wailing Souls. A large shadowy beam will appear in front of the Devourer, and make a 90 degree sweep of the room. Anyone who is caught in this beam will take about 10,000 damage a second, so it is imperative that everyone moves out of the way of this ability immediately.
Loot: Normal Mode, Heroic Mode (via WoWhead).