The Sixth boss of Karazhan and also the equivalent to a benchmark or skill check on many raids given his unique nature and the rather difficult elements that construct this boss fight, including what is ultimately a mad mage running loose on your raid.

Spells

These are the three spells that are used repeatedly by the Shade as his general damage attacks.

Fireball – Deals somewhere around 4000 damage.
Frostbolt – Deals about 3000 damage and applies a chill effect that slows down the player, also dispellable.
Arcane Missiles – Deals around 1500 damage per volley of bolts for a total of 4 volleys per cast.

Counterspell

The shade will utilize an AoE counterspell ability every 8 seconds that shuts down any schools of magic being cast by raid member within ten yards of the boss.  Have DPS and healers keep their distance.

Ice Chains

Similar to a shackle spell, this chains down one player in place and prevents all movement.  Magical and therefore dispellable, get rid of this as otherwise the affected player can get hit by the bosses AoE attacks.

Special Abilities

These spells are indicated to their usage by the Shades movement towards the center of the room as well as his dialogue that should allow you to know what spell he’s actually going to use.  Pick up on the dialogue and react as fast as possible.

Mass Slow + Arcane Explosion

This begins with all members of the raid being sucked in towards the Shade and debuffed with a mass slow spell, lowering movement speed dramatically.  The Shade will then begin to cast Arcane Explosion.

As soon as the spell is begun everyone needs to be getting out of range and hiding away as far as possible to avoid a potential of 10,000 or more damage from this massive attack, run for nooks and corners if needed, if you have to dispel the slow while your running to speed up a bit.

Blizzard

This will cause icicles to begin falling somewhere within the library, indicating the positioning of where Blizzard will start.  This spell will continue to move in a clockwise path around the outside of the room, requiring all the ranged DPS and healers to move according to the blizzards path or risk 1200-1500 damage per tick and a slowing effect.

Flame Wreath

This is probably the most dangerous and equally most interesting of the Shades abilities, being quite the raid wiper especially on your first or second tries of the boss.  Once this spell is cast several raid member will be debuffed with the Flame Wreath effect, do not move whatsoever.

Moving whilst under the effect of this spell causes everyone nearby to explode and take somewhere around 4000 damage, very ugly when you’re next to a number of players.

Summoned Water Elementals

Once the Shade reaches 40% health he’ll summon four water elemental guards around the outside of his room.  Each Elemental lasts for 90 seconds and has around 13,000 HP, additionally they each fire water bolts for 1000-2000 damage each hit.  These are fearable and banishable.

Mass Pyroblast + Polymorph

Once the Shade drops to low HP and if his mana is below his health he will require a drink to regain mana.  At this point the boss will Polymorph the entire raid, mass sheep, and sit down to drink.  Upon standing up once more and having topped off his mana supply the Shade will cast an instant Pyroblast that deals around 6000 damage to everyone in the raid.

Enrage

Should you take this fight over the fifteen-minute timer then the boss will immediately explode spells everywhere and wipe your raid, the fight shouldn’t take that long however.

Fight

This fight is all about dealing with the Shades massive spells and interrupting everything possible, have everyone turn on the enemy cast bars for this fight as seeing what he’s casting is imperative to fighting this guy.

To start the fight I recommend having a warrior charge in and take his aggro, this makes it so that the first spell is targeted at the warrior and allows him to interrupt the Shades casting as well, if he can’t then the toughest member of the raid gets hit, not much to worry about.
Everywhere from three to five interrupters is probably required for this fight, however four is probably the average for somewhat experienced Karazhan runners and five or more for first timers on this boss.

Divide your interrupting squad into groups to take care of Fireballs, Frostbolts, and have them in a specific execution order or grouping to deal with each spell to prevent needless interrupts being used on one spell.

Make certain that each member also knows to call out resists, misses, and so on when using their interruption attacks, if this happens another player should be ready to immediately step in and knock the spell down instead.

Rogues, Mages, Warriors, and Shamans all need to conserve mana, rage, or energy to allow them to interrupt spells via kick, pummel, earth shock, or counterspell as needed, don’t waste your abilities on DPS when you need them to interrupt.

Throughout the fight the Shade will continually stop casting his normal spells and proceed to unleash one of the massive spells listed above, always have everyone well coached on how to deal with each spell or even one mistake can wipe the raid, especially on Flame Wreath.

Additionally, when the Shade is wandering about the room your melee will have to be quick on chasing him down to DPS, interrupt spells, or whatever they happen to be doing, keep directly on the boss at all times unless he’s about to unleash a spell.

Once the Shade reaches 40% health he unleashes four water elemental guards that appear at the corners of the library.  At this point you have a number of methods available to deal with this annoyance, one is to banish and fear them, another is to simply burn them down should the danger or healing requirements be too much.

When the elementals spawn you might also have to deal with a blizzard or other such spell which can make dealing with the problem quite troubling as you get pummeled from multiple enemies.  Either way you have to handle the elementals somehow or just get run over by the combined forces.

Finally, keep a supply of healthstones and potions ready for the massive pyroblast following a mass polymorph and drink, this prevents your healers from needing to waste mana on healing the entire raid and instead can focus once more on what is absolutely necessary.