Fathom-Lord Karathress
The Basics
This section contains a basic outline of the fight, and is a must read for everyone, as it contains information you need to know so as not to wipe the raid. If you are interested in knowing the why of the instructions here, or in improving your individual performance, the details are available below.
Karathress is a fight with three adds, each of which is killed in turn, then we kill the boss. Keys to this fight are fast target switching, and interrupting the healer add. As each add is killed, Karathress gains one of their abilities, which will need to be dealt with. There will be five tanks, one for each of the mobs, and one for the pet when summoned.
Karathress' three adds are Tidalvess, a shaman, Sharkkis, a hunter, and Caribdis, a healer. Our kill order is Tidalvess, Sharkkis, Sharkkis' pet (if it is the bat), Caribdis, and then Karathress himself. On the pull, Karathress will be misdirected to a tank in the buffing area, who will move him to the corner on that side. Caribdis will be taken to the opposite corner, and Tidalvess and Sharkkis will be tanked together, and the pet tank will prepare to pick up Sharkkis' pet as soon as he casts it.
Karathress will from time to time cast Cataclysmic Bolt on a random member of the raid who has a mana bar. This bolt does half your maxiumum health in damage.
Caribdis will attempt to heal her fellow adds anytime they get lower than about 60% on health. Her heal is a very fast cast, so she must be slowed with either mind-numbing poison or curse of tongues. When an add reaches 60%, the interrupters assigned to her must keep their global cooldowns free to interrupt the heal.
Sharkkis has an ability called Leeching Throw which is a mana drain.
Getting Tidalvess down fast is vital to this fight. As a shaman he has windfury, and a frost shock which he uses on his tank for immense burst damage. He must be kept debuffed with tclap and demo, and a grounding totem kept down for the tank to absorb as many of the frost shocks as possible. Tidalvess casts totems from time to time, the only one the raid needs to concern itself with is the Spitfire Totem, which will do serious damage if not nuked immediately. All DPS on Tidalvess must switch to and kill the totem as soon as it is cast.
Once Tidalvess is down, the healers for that tank disperse to help out with the others, and the raid works on Sharkkis. When Tidalvess is killed, Karathress gains Tidalvess' Spitfire totem, and the tank and healers on Karathress will begin moving to outrange the totem each time it is cast.
When Sharkkis dies, Karathress gains his Beast Within skill, which increases his damage when he gets big and red (that's what she said). Once he is dead, if his pet is the bat, the raid will kill it (the elemental will eventually just blow up, the tank can remain with a healer) and then go down to Caribdis, and kill her. Once she is dead, Karathress gains her Tidal Surge ability.
When the raid moves to Karathress, that group stops moving to outrange the Spitfire Totem and the raid will once again be fast target switching to kill it.
The Details
Karathress:
Health: 1.7 million
Enrage timer: 10 minutes
Base damage: 2.2K to 3.5K on tank class armor, weapon speed 2 seconds
Immunities: all crowd control, taunt
Special abilities:
Cataclysmic Bolt: targetted at random mana user, half their maximum health in shadow damage, short stun, 7 second cooldown
Sear Nova: Melee range
AoE, does about 2.5K to 4K fire damage, 15 to 20 second cooldown
Power of Tidalvess: Gains this when Tidalvess dies, allows him to cast the Spitfire Totem
Power of Sharkkis: Gains this when Sharkkis dies, allows him to cast Beast Within
Power of Caribdis: Gains this when Caribdis dies, allows him to cast Tidal Surge
Tidalvess:
Health: 840,000
Base damage: 3K to 4K on tank class armor, weapon speed 2 seconds
Immunities: all crowd control, taunt
Special abilities:
Windfury: gives two additional attacks when procs
Frost Shock: 6K frost damage
Spitfire Totem: 25000 health, pulses 3K fire damage on up to five raid members every three seconds, 45 yard range, not
LoS'able
Poison Cleansing Totem: attempts to remove one poison effect every five seconds
Earthbind Totem: Reduces movement of nearby raid members by 50%
Sharkkis:
Health: 850,000
Base damage: 1.5K to 2K on tank class armor, weapon speed 2 seconds
Immunities: all crowd control, taunt
Special abilities:
Hurl Trident: only if his aggro target is not in melee range, 1.5 to 2K on tank class armor, typically only seen on the pull
Multi-Toss: a multishot ability that hits up to three raid members, 2K to 4K, depending on armor
Leeching Throw: A mana drain dot, 525 health and mana every 2 seconds for 12 seconds
The Beast Within: increases his damage by 30% and his pet's by 50%
Summon Pet: He can summon one of two types of pet:
Fathom Lurker: an elemental type pet, does about 2K to 2.5K melee damage, blows up after awhile, so tank it away from the raid, not CC'able
Fathom Sporebat: beast type pet, does about 2K to 2.5K melee damage, not CC'able, has about 240,000 health
Caridbis:
Health: 880,000
Base damage: 1.8K to 2.4K, weapon speed 2 seconds
Immunities: all crowd control, taunt
Special abilities:
Water Bolt Volley: 2.4K to 3.2K frost damage to all within 45 yards
Healing Wave: Heals for about 20% to 30% of the target's total HP, interruptable, very fast cast, about one second cast time, 15 second cooldown
Tidal Surge: Freezes players within 10 yards range for 3 seconds, 1.5K to 2K frost damage
Whirlwind: A tornado like effect that targets a random player and slowly moves towards them, changing targets frequently, throws player in the air
and puts on a debuff that slows casting speed
Managing Tidalvess
Tidalvess is easily the most dangerous mob in this fight, exceeding Karathress' damage potential easily. His windfury attack combined with the frost shock can easily kill a tank very quickly, and the Spitfire Totem can nuke the raid heavily if not dealt with quickly. All available methods to reduce his damage must be employed. Thunderclap, demo, grounding totem, and scorpid sting are vital. The raid must switch to DPS'ing the totem immediately, combo points or not.
Managing Caribdis
Caribdis' heals must be interrupted, and our typical strat would be to use a warrior tank, a rogue, and a mage (cuz we ain't got an elemental shaman). The rogue will shiv mind-numbing poison to slow her cast time. Once the mob being DPS'd reaches 60%, the interrupters must keep their global cooldowns free when she may cast, keeping in mind the 15 second cooldown. Because of the Tidal Surge, it is possible for both melee interrupters to be frozen when she casts, so the mage will save his counterspell to use if she tries to heal while the melee are frozen. Allowing her to cast heals not only risks hitting the enrage timer, but the healing required for more DPS time is not sustainable, especially while Tidalvess is still up.
"Why don't we just kill Karathress before he gets all those abilities?" If Karathress reaches 75% health with any of the adds still up, he receives a stacking buff from each called Blessing of the Tides, each stack increases his damage and attack speed by 65% and reduces the cooldowns on his abilities by 65%. If you do the math, you can see that the increased damage on Cataclysmic Bolt alone makes this undoable.
"Why do we use the kill order we do?" Tidalvess is easily the most dangerous and requires three healers. Killing him first releases those healers to help out elsewhere. The fight almost becomes trivial as soon as Tidalvess is down, so he goes first. Sharkiss dies next, because we tank him next to Tidalvess so that classes with multitarget abilities can use them, and thus he already has a fair amount of damage done to him when Tidalvess dies. He also has that annoying mana drain that can make things problematic if he targets lots of healers with it. We don't kill his pet first because he will just resummon it. Caribdis is easily made mostly harmless with a good crew assigned to her, so she goes last.
"When should I use cooldowns for more DPS?" Getting Tidalvess down is the key to this fight, definitely use them on him. Rogues should definitely use blade flurry once Tidalvess and Sharkkis have been positioned next to each other. It typically takes about two minutes to kill Tidalvess, so don't feel like you have to pop off immediately, be mindful of tank threat. A good time for Heroism would be right after the first Spitfire Totem is killed, for instance.
"Who should I prioritize if I'm a raid healer?" If the Spitfire Totem gets a volley off, prioritize mana users who get hit first, because they are the only ones who will be targetted by the Cataclysmic Bolt, and the only ones who will get hit by the Leeching Throw. Any warriors, rogues, and feral druids, you have about 25 seconds until the next Spitfire is plonked down to get healed up. If you make Karathress your focus target, and use an addon with a focus frame and show target of target, you can see exactly who Karathress is targetting for the Cataclysmic Bolt before he casts it. You can expect a Cataclysmic Bolt every 7-15 seconds, a Leeching Throw about every 20 seconds, and a Spitfire Totem to go down about every 25 seconds.
"Why do we do the pull this way?" Typically, our Tidalvess tank is a paladin, and thus subject to getting hit by the Cataclysmic Bolt. We have found that Karathress up in the corner and Tidalvess where he stands puts that tank out of range of the Cataclysmic Bolt. Caribdis is tanked in the opposite corner from Karathress so that group won't get hit by Cataclysmic Bolt, and will be out of range of the Spitfire Totem once the Karathress group begins kiting away from it.
"You can outrange the Cataclysmic Bolt, why don't we do that for the whole raid?" Because then his only possible target would be the Karathress healer, and require that we use two healers on Karathress to start. We don't run with eight healers, so we spread the Bolt out over as much of the raid as possible. Our initial heal setup is three healers for Tidalvess, one each for Caribdis and Karathress, one for Sharkkis and the pet, and a raid healer who helps out on the pet tank.