The lich Lady Deathwhisper is the Supreme Overseer of the Cult of the Damned and the second boss of the Icecrown Citadel raid. The fight is mostly a DPS race (with a high damage output it becomes significanty easier), but also requires high awareness from all raid members.
PHASE ONE ONLY
Animate Dead - Reanimates a Cult Adherent or a Cult Fanatic.
Dark Empowerment - 200 yd range—Empowers the Cult Adherent's spells, causing them to deal area damage and making them uninterruptable. 2 sec cast.
Dark Transformation - 200 yd range—Transforms one random Cult Fanatic into an undead behemoth, increasing damage dealt by 100%. 2.5 second cast.
Mana barrier - Envelops the caster in a powerful barrier that continually replenishes any lost health, at the expense of the caster's mana.
Shadow bolt - Sends a shadowy bolt at the enemy, causing 11813 to 13187 Shadow damage. 100 yard range. 2 seconds cast.
PHASE TWO ONLY
Frostbolt - 40 yd range—Inflicts 50,700 to 53,300 Frost damage to an enemy and reduces its movement speed by 50% for 4 sec. 2 sec cast. Interruptable but unresistable on heroic difficulty. 58,000 to 61,000 on Heroic.
Frostbolt Volley - Inflicts 14400 to 17600 Frost damage to nearby enemies, reducing their movement speed for 4 sec.. Instant.
Touch of Insignificance - 50,000 yd range—Reduces the target's threat generation by 20%. Instant. Stacks to five. Lasts 30 seconds
Death and Decay - (Heroic Mode) 4500 Shadow damage inflicted every 1 sec to all targets in the affected area for 10 seconds. Instant. 8 yd radius. 6000 on Heroic
This Phase is all about killing the adds quickly and efficiently. Ranged DPS in particular need to switch their target frequently, and be highly aware of the general situation.
Phase 1 ends as soon as her mana shield is down. During the phase, all damage she takes is deducted from her mana, Phase 2 starts as soon as it reaches zero. Phase 1 should not take longer than 7 minutes, else there won't be enough time to kill her prior to the enrage.
During Phase 1 she needs no tank. She spams Shadow Bolt, Death and Decay and Dominate Mind on random raid members (Dominate Mind is only cast in 25-player mode, it affects one raid member in normal mode, and multiple targets in heroic mode). The mind controlled raid members need to be Crowd Controlled.
Also randomly, she places Death and Decay, and AoE DoT. Raid members need to move out of this quickly.
After 5 seconds of combat and every 60 seconds thereafter 3/7 (10/25 player) adds spawn. In 10 player, 3 adds spawn alternatively from the three gates on the left and right side. In 25 player, 3 adds spawn on each side every time, and a seventh add of a random type spawns on the stairs. The three gates on the left side of the room always spawn two fanatics and one adherent, the right side gates one fanatic and two adherents. All types of adds can be CC'd.
Living adds can explode (dark martyrdom) at random times, which deals AoE damage and turns them into their reanimated versions. Reanimated Fanatics (melee) are immune to physical damage, Reanimated Adherents are immune to magical damage. Also at random, Lady Deathwhisper buffs living adds. Buffed Adherents become "Empowered Adherents", adding an uninterruptible AOE spell to their abilities, buffed Fanatics are "Deformed Fanatics" and double their melee damage output. These four special add types are the most dangerous, and must be killed as priority targets.
Adherents are caster mobs who spam deathchill bolt, put a cooldown increasing curse on random players, and sometimes shield themselves with a spell reflect shield. The shield (Shroud of the Occult) takes 50,000 damage to remove. While the shield is on them, silencing effects like [Shield Bash] do not work.
Fanatics have a high melee DPS output and a vicious cleave (melee DPS must take care to stand behind them). When buffed (as Deformed Fanatics), they double their damage output. Deformed Fanatics should be kited, which is quite easy because their movement speed is halved. Fanatics (either normal or deformed) are sometimes buffed with Vampiric Might which is another 25% damage increase, plus a self heal for 3x the damage they cause. This can (and should) be removed with a Shaman's [Purge] or a Mage's [Spellsteal]. Spellsteal is the preferred method since it benefits the Mage.
Any adds present when the mana shield is depleted stay up for phase 2. If an add wave was about to spawn it may still spawn after Phase 2 started. If such a situation is likely to develop, stop DPS should be called.
The basic method described above is to assign the tanks to the spawn locations. The left and right sides also get a fixed set of melee damage dealers (more to the right side, fewer to the left). When adds spawn, all ranged DPS switch and kill the adds right where they spawn. After all adds are dead, all damage dealers switch back to the Boss, a few seconds prior to the next wave, melee run back to the spawn locations.
This method feels rather natural and it leads to a distributed setup, which helps minimizing the effect of Death and Decay. The drawbacks are rather low DPS (particularly by melee), and frequent target switching.
With some practice, melee can concentrate on the caster adds, and ranged help on the melee adds, if overall DPS is high enough, ranged need to switch only if one of the special adds comes up. Adherents can be gathered by Line of sight pulling, using the nearby walls.
Because of their heavy reliance on DoTs, Affliction Warlocks and Shadow Priests might be more useful if they're assigned to continually attack the boss, and only attack the adds in cases of emergency, as burst damage tends to bring the adds down fairly quickly.
After her shield is down, Lady Deathwhisper switches to a new set of abilities, she gets an aggro table (in effect her threat is reset) and also starts to melee and cast Frostbolt volley. No more Adherents or Fanatics spawn, instead Vengeful Spirits randomly spawn near players.
Her Frostbolt spell should be interrupted. Dominate Mind and Death and Decay continue as before. She stacks an ability called Touch of Insignificance on her tank. This reduces threat generation by 20% per stack (stacks to 5). On normal difficulty, she can be taunted. The standard tactic (on normal mode) is for the tanks to taunt her off each other to allow the debuff to fall off. In theory a single tank can keep her by using taunt on every CD, but this is only a short-term solution as diminishing returns ensures that she eventually becomes taunt-immune.
Vengeful Spirits pick a random target and follow it for 10 seconds, they explode for 25,000 shadowfrost AoE damage when they catch up. In normal difficulty it's possible to heal through this, in heroic mode probably not. Players targeted by a Vengeful Spirit need to kite it until it goes away.
Other than every ability simply hitting harder the main difference in the encounter that may encourage groups to alter their strategy is a shortened enrage timer and doubled hit points (but not mana) on Lady Deathwhisper thus extending phase two.
The heroic encounter is similar to the M'uru encounter. Raids probably cannot focus all DPS on adds because more damage must be done on Deathwhisper. It seems likely that Crowd Control may be needed on at least some of the adds through the entirety of phase 2 in order to beat the enrage timer, at least until the encounter is outgeared.
Confirmed live heroic mode differences:
Immune to taunt.
One/Three mind controls (10/25 player).
Adds continue to spawn in phase 2.
Vengeful Shades explode in a 20 yard radius instead of single target.
One novel strategy is to have one tank kite the Fanatics around the room for the entirety of the fight much like the Razorgore the Untamed encounter in Blackwing Lair since they are affected by all movement impairing effects.
[info from http://www.wowwiki.com/Lady_Deathwhisper]
Lady Deathwhisper 10 MAN video below: