Anetheron is the Dreadlord commander assigned to personally accompany Archimonde on his assault into Azeroth, etc.  This guy was seen in Warcraft 3 as are most of the bosses in Mount Hyjal as well as some of those inhabiting various other instances such as The Eye, Serpentshrine Cavern, and even Black Temple.

Abilities

4,200,000 HP

Melee – Averages 3,000 – 6,000 on plate.

Carrion Swarm – A green carrion wave fired in a large cone directed towards a random target.  Deals 4250 – 5750 shadow damage accompanied by a debuff that reduces healing ‘Done,’ not received as with mortal strike/other such effects, by 75%.  Debuff lasts 20 seconds and the spell itself possesses a 60 yard range, used every 10-15 seconds.

Inferno – Summons a towering infernal to fall from the sky and smash into the ground upon a random target, dealing 2,500 fire damage and stunning the initial target. 

The summoned infernal itself has 220,000 health as well as an immolation aura dealing 3325 – 3675 fire damage every 2 seconds to all players within 8 yards.

Sleep – Sleeps up to 3 players at a time for a total of 10 seconds, removable via tremor totem, Will of the Forsaken racial.

Vampiric Aura – Will heal Anetheron for 300% of his damage dealt, countered partially by rogues wound poison(50%,) also applies to the summoned infernal if within range.

Fight

After clearing your obligatory 8 waves of trash as per the previous fight you’ll finally be given a chance to drop another boss, Anetheron.  Basics of this fight will lie in the positioning, that being primarily due to the odd debuff effect of Carrion Swarm, a 75% reduction in ‘your’ healing done.

If all your healers are hit by this it’s pretty much a wipe, therefore you’ll want to spread them out widely enough to avoid any given healer being targeted with the spell resulting in its rather wide cone of effect reaching other healers.

As you’ll need a tank for both the infernals as well as the boss himself healing becomes doubly important, even moreso enhancing the need to remain at a normal healing level and away from the carrion swarm debuff.

Aside from that you’ll be dealing with both random sleeps, meaning it would be best to have at least 2-3 healers standing nearby a tremor totem at all times, as well as the infernals plummeting from the sky.

Paladin tanks are the best bet for the job of picking up stray infernal spawns, exorcism and avenger’s shield both work excellently as a ranged threat tool allowing healers to continue their work without fear of a raging infernal running rampant on them, the infernals immolation aura makes it doubly important to keep it out of the raid group.

Overall you’ll find your greatest challenge being the healing debuff effect, maintain a few un-debuffed healers at all times and you’ll most likely cruise through the fight without falling off the edge of defeat.