Fathom-Lord Karathress

Fathom-Lord Karathress can be found in Serpentshrine Cavern and is usually killed as the fourth boss. The fight involves several adds (similar to High King Maulgar), and is a battle for survival which is made much easier by high DPS. After killing Karathress,, his prisoner is freed and adventurers can now talk to him.

Fathom-Lord Karathress

 * Cataclysmic Bolt: Targets random mana user, deals 50% of target's max HP in shadow damage (increased by The Beast Within), a brief knockdown and a stun. Resistible binary spell. 6 second cooldown. Targets only players with mana bars.
 * Melee: rather low at first, increases to ~6,000 on plate after gaining "The Beast Within"
 * Sear Nova: ~3,000 fire damage melee range AoE, cast every 20–60 seconds
 * Blessing of the Tides: If Karathress reaches 75% health while any of the three adds is still alive, he gains Blessing of the Tides, increasing both cast time and attack speed by 66% for each add still alive (= triple damage output with 3 adds up)
 * Enrage : 10 minute enrage timer

Fathom-Guard Sharkkis

 * 855,000 HP
 * Melee: normally only moderate damage (until The Beast Within, see below)
 * Multishot : ~2000-3000 damage on three players
 * Leeching Throw: similar to Viper Sting this randomly targeted attack burns mana and health at a rate of 525 per tick for 12 seconds
 * Hurl Trident: hits a random target for ~1500
 * Summon Pet: Sharkkis summons a non-CCable pet, either an elemental (Fathom Lurker) or a beast (Fathom Sporebat). The pet deals simliar amounts of melee damage as Sharkkis himself. The elemental pet explodes when killed, the beast doesn't. The Sporebat has a knockback reducing the tank's threat on it.
 * The Beast Within: from time to time, Sharkkis turns red for 18 sec. increasing his damage by 30% and the pet damage by 50%

Fathom-Guard Tidalvess

 * 840,000 HP
 * Shaman Abilities: Tidalvess has Windfury Weapon and a Frost Shock for 5400-6600 Frost damage.
 * Totems: He can summon one for the following totems:
 * Spitfire Totem - 25.000 health, 1 min duration, periodically attack up to 5 players within 45 yards for 2550-3450 Fire damage ignoring line of sight
 * Poison Cleansing Totem - 4000 health, removes 1 poison effect from Tidalvess every 5 seconds
 * Earthbind Totem - lasts 45 sec., periodically reduce movement speed of nearby players to 50% of normal

Fathom-Guard Caribdis

 * 885,000 HP
 * Water Bolt Volley: 45 yard AoE dealing 2775-3225 Frost damage, resistible
 * Healing Wave: Single target heal unrestricted by LoS or range, cast on any mob or herself, heals 20-30% of the target's total HP. Interruptible, 15s cooldown
 * Tidal Surge: every 10–15 seconds, 10 yard AoE stun (players are frozen in an ice block) for 3 seconds. No aggro reset, resistible
 * The Whirlwind: From time to time, a whirlwind spawns near Caribdis, which moves all over the whole room. It deals no damage, but lifts players up in the air for about 3–9 seconds and gives a debuff which increases cast time

Raid composition

 * 2 main tanks
 * 2-3 off tanks (e.g. feral druids or DPS warriors in tank gear)
 * 7-8 healers
 * 8-10 ranged damage dealers
 * 2-5 melee damage dealers

The group with the Tidalvess (Shaman) tank should contain a shaman, who keeps Grounding Totem up at all times, to negate Tidalvess' Frost Shock.

Due to the mechanics of Fathom-Lord's Cataclysmic Bolt, paladin tanks are not advisable for this fight. Damage caused by this ability to a tank with ~18-20k health is very difficult to heal through and can easily cause a wipe for entire raid.

Kill Order
Since Blessing of the Tides is a rather evil buff for the boss, it's reasonable to kill the adds first. The priest is the easiest add to control and should be killed last. Whether the shaman or hunter has to be killed first is a matter of choice. The hunter drains mana, the shaman deals the most damage - if the two main tanks both have good gear, it may be better to kill the hunter first. The following kill order minimizes the damage taken by the raid:
 * 1) Tidalvess (Shaman add)
 * 2) Sharkkis (Hunter add)
 * 3) Caribdis (Priest add)
 * 4) Karathress (boss)

Every time an add dies, Karathress gains a new ability (similar to the Anubisath Mobs in the Temple of Ahn'Qiraj):
 * When the shaman's dead, Karathress starts to drop the same "Spitfire Totem" as the Shaman
 * After Sharkkis the hunter dies, Karathress permanently gains "The Beast Within", greatly increasing his melee damage output
 * From Caribdis the priest, Karathress gains "Tidal Surge" (10 yard AoE ice block freeze every 15–20 seconds)

Positioning
First the entire room and the patrol in the next passageway must be cleared. Tanks list:
 * Karathress - best geared main tank
 * Tidalvess - 2nd main tank
 * Sharkkis - offtank
 * Sharkkis pet - offtank (possibly the same as the Sharkkis offtank, if well geared)
 * Caribdis - warrior offtank

The shaman and the priest both have a 45 yard AoE spell. After the shaman's dead, Karathress gains that ability from the shaman. Thus the best setup would be to have the boss, the shaman and the priest all 45 yards apart from everybody else. Unfortunately such a setup has not been found so far, so usually the priest add gets a small group in one corner, the boss is tanked near his initial position, while the hunter and the shaman are killed away from the other mobs.

On the pull, Misdirection is best used on the Shaman add (to prevent him from taking out the Karathress tank with a damage burst), on all other mobs it's optional.

Spitfire Totem
During the whole fight, the spitfire totem is a major source of raid damage. While adds are still up, it's absolutely necessary to bring it down ASAP when it spawns. All ranged damage dealers should have a macro to quickly target it i.e. /target Spitfire Totem. When only Karathress remains, it's possible to ignore the totem and simply heal through the damage.

Caribdis Group
One warrior off-tank, a rogue and a shaman healer is the smallest group able to control Caribdis. Adding a warlock, a mage or an additional healer makes the job easier, but also slows down the killing of the other adds and/or makes raid survival more difficult.

The purpose of the priest add group is to interrupt all her heals. The rogue should use Mind-numbing Poison. When the two melee classes are frozen, the shaman healer must pay extra attention to be ready and use rank 1 Earth Shock when she starts a heal.

Adding more melee damage dealers to this group is pointless, it only increases the load on the healer. If heals keep getting through, a warlock may keep Curse of Tongues active on her, and if the warrior or rogue die frequently it helps to have a second healer paying attention to this group. The healer's job is easier if this group can stay 45 yards away from all other mobs, so that the random damage spells from the other mobs don't interfere.

Quotes
Aggro: Killing a player: Killing Caribdis, Sharkkis, or Tidalvess: Misc: Upon Gaining Blessing of the Tides: Death:
 * yell
 * yell
 * yell
 * yell
 * yell
 * yell
 * yell
 * yell
 * yell

Soloing Fathom-Lord Karathress
Fathom-Lord Karathress is one of the most annoying encounters that ramps up in difficulty (due to Fathom-Guard Sharkkis summon a pet every now and then) until Fathom-Guard Carabidis is killed. It can take quite a few tries to master. In addition, without a reliable interrupt ability on a short cooldown such as Mind Freeze, this encounter is impossible to solo due to incoming Healing Waves.

Start the encounter by attcking Caribidis. You must kill her before you can kill any of the other members of the group. When her health starts to dip towards 300k, she will cast a Healing Wave (1.5 second cast, 15 second cooldown), which heals for a little more than 100k health. You have to keep interrupting that to kill her. In addition, she summons a Whirlwind that moves around the room. You will have to kite the group away from it. You can get very easily caught in the Whirlwind as one of the group members constantly knock you back, reducing your control over movement. When that happens, you will be out of range to interrupt Caribidis' Healing Waves should she cast it.

If your damage is high enough, to work around the healing Caribidis does, attack one of the pets that Sharkkis summons and bring it down to near 50% health. Caribidis will always heal the target with the least percentage of health, this, she will heal the pet. Still, it is advisiable to keep interrupting her (Every interrupt will thus not require you to damage a pet) as the longer you take to kill her, the higher the rate of damage taken (due to increasing numbers of summoned pets).

Once Caribidis is killed, start killing all the pets that Sharkkis has summoned. Once all the pets and Carabidis are dead, the fight becomes very easy. Even when Karathress has the Blessing of the Tides and all guards dead, conferring him new abilities, he is still a pushover. Next up, kill Sharkkis, followed by Tidalvess and finally the Fathom-Lord himself.

He drops 250 gold, 3 Tier 5 tokens and 1 epic item.