Jormungar Behemoth

Jormungar Behemoth is an elite jormungar found in Ulduar. Although not technically a part of a boss fight, killing the Jormungar Behemoth and the surrounding adds will trigger the start of the event that leads to the boss fight with Thorim.

Players attempting to defeat the Jormungar Behemoth should face it away from the raid.

Abilities

 * Acid Breath: spews acidic bile at a target and nearby enemies, inflicting 6000 (normal) or 12,000 (heroic) Nature damage and 1500 additional damage every 2 sec. for 18 sec.
 * Sweep: sweeps at the legs of an enemy, dealing 6000 damage and causing knockdown for 3 seconds. Melee range, instant cast.

Trivia
According to its race and abilities, the Jormungar Behemoth is probably a reference to Thor's killer: The Jörmungandr.