Shade of Eranikus

Shade of Eranikus is a level 50 elite (55 elite prior to patch 2.3) ghostly dragon boss found in the Temple of Atal'Hakkar. In order to be able to attack Eranikus, you must first defeat Jammal'an the Prophet and then the two drakes that spawn afterwards.

Background
The great Emerald Wyrm Eranikus was dispatched by Ysera, the Dragon Aspect of the Emerald Dream, to deal with the growing troll threat in the Swamp of Sorrows. Unfortunately, Eranikus was possessed and corrupted by the Old Gods and now is a malevolent force in the Sunken Temple.

Strategy
Before you start, make sure you have killed all four dragonkin minibosses, or they will join the fight.

Shade of Eranikus is a sharp step up in difficulty from the other bosses. Eranikus has a strong melee attack that can make quick work of any non-tank class, so it's imperative that Eranikus be on a tank at all times. This is complicated by Eranikus' ability called Deep Slumber which is a twelve second stun (rather than a sleep effect despite it's name). While it is a magic effect, it also makes the target invulnerable to all spells and abilities. Having two tanks eases this fight tremendously as the off tank can simply taunt Eranikus whenever the main tank has Deep Slumber and hold him until the main tank is back in action. This can get complicated, however, as Eranikus also has a four second AoE stun similar to War Stomp which he uses on a separate timer from Deep Slumber. Eranikus will still attack anyone hit with this War Stomp, but if the off tank is stunned before he can take over during a Deep Slumber, things can turn ugly, and the rest of the group should take whatever measures are necessary to control Eranikus (e.g. Blessing of Protection, Ice Block, etc.) until a tank becomes available. A shaman is also a tremendous asset to this fight when using Grounding Totem. Deep Slumber can and will be intercepted by the totem, and since Deep Slumber is the only non-AoE spell that Eranikus uses, Grounding Totem will effectively "tank" the Deep Slumber for the entirety of the fight, making it a simple Tank and Spank.

Shade of Eranikus has a knockback attack that can send a player flying. If the maintank runs straight past Eranikus to stand with his back against the back wall, this can be nullified, yet care must be taken that the knockback does not put the player with aggro up on the ledge around the wall. This will put the player out of range of any of Eranikus' attacks, forcing him to enter an auto-evade mode and regenerate health at a huge rate. If a player is knocked up onto the wall, they must drop to the ground immediately or risk having to restart the fight.