Olm the Summoner can be found in Gruul's Lair .
Deathcoil 2000 damage, heal himself 4000, Dark Decay 500 per tick, attack 1800 on plate, summon felhounds. Should use warlocks to enslave the felhounds to tank him. He has deathcoil, so best tank with 2 felhounds.
If the locks wish to use a macro to CC the fel hounds then the actual name of the fel hounds is: Wild Fel Stalker
Can cast Dark Decay DOT without line of sight, but needs LOS to Death Coil. Not immune to taunt.
Hits for ~3.6k crushings on ~11k armour.