The lurker below, although officially second boss of Serpent Shrine Cavern, is generally killed first by those still new to the dungeon, being far easier than the actual first boss, Hydross, a situation rather similar to that of The Eye, Al’ar/”Loot Reaver.”

Abilities

Melee – Hits for around 5,000-8,000 on plate.
Whirl – AoE physical attack to all within melee range, 3,000-4,000 damage, 5 yard knockback effect, 30 second cooldown.
Geyser – Randomly targeted attack on ranged player, 3,500 frost damage AoE with a 10 yard knockback to those within range.
Spout – Deals around 6,000 damage accompanied by a large knockback effect.

Submerge – Every 120 seconds, counting down from entering combat, the boss will submerge, removing all debuffs and summoning adds, Phase 2 begins, the boss re-emerges 60 seconds later.

Water Bolt – Only utilized when no target is in melee range, 2 second cast time, 9,000-11,000 damage, randomly targeted.

Phase 1

Phase one begins with the initial combat against Lurker on the surface, this is basically a straightforward tank n’ spank fight, the only exceptions being the whirl and spout abilities the boss will utilize.

Spout

An incoming spout should be given a warning by applicable boss mods, giving your raid enough time to escape by leaping into the water, ranged/healers can continue to attack/heal further into the water as melee approach lurker and re-engage.

Spout can also be negated by Ice block, Divine Shield, blinking through it, and a variety of other evasion methods, however it’s always easiest to just jump in the water and leave no room for error.

Whirl

Whirl is only a problem due to Lurker’s ability to quickly drop players at range should he have no targets within melee distance, allowing him to do so can easily be crippling.

Deal with this by either A: Having your main tank yet again hit the water, coming closer to lurker and therefore when eating the knockback simply returning to the platform, or B: Running out of range quickly before returning immediately after the whirl has been utilized.

Having another tank to help make certain this goes smoothly can never hurt, however after a few runs of this boss it should be fairly simple to accomplish with only one.

Phase 2

Phase 2 will begin after 120 seconds, Lurker submerges and summons a total of 9 adds, 2 Coilfang Ambushers per outer platform, 6 total, and 3 Coilfang Guardians on the inner ring.  Thankfully these are all susceptible to crowd control.

To deal with this make certain you have groups of primarily Ranged DPS assigned to specific platforms, given the duty of clearing this first before possibly aiding others should this be required.  Melee can work on the 3 Coilfang Guardians and attempt to drop them before the boss returns.

In general even if an add or two is still up when Lurker emerges, it’s easy enough to keep them under some form of crowd control before dropping them sometime during the phase, just keep an eye on the add’s lest they run free while dealing with Lurker.