The Four Horsemen

The Four Horsemen is the final encounter in the Deathknight Wing of Naxxramas. The encounter requires that players manage the four bosses, Thane Korth'azz, Highlord Mograine, Sir Zeliek, and Lady Blameaux, all at the same time. The encounter is famously challenging, and requires that the raid group have seven to eight tanks in total, four with high level gear and three to four who can manage the bosses while the 4 main tanks rotate. The entire raid needs to be extremely careful of positioning, paying attention to each boss' mechanics, and rotate throughout the room at a scheduled pace to not acquire too many marks from each of the bosses.
Overview
Tank
Eight tanks are required for this fight, one for each of the Horsemen, and another to take over tanking each Horsemen while the main tanks are rotating. On pull, it is essential that each of the horsemen is positioned in their respective corners of the room. Utilize [Disarm] against the bosses in this encounter.
Damage Dealers
Melee DPS need to move between their safe spot and the boss that they are assigned to. When damaging Korth'azz, stack up to avoid taking solo damage from [Meteor]. When damaging Blameaux, be aware of the [Void Zone] which spawn on the ground. When attacking Zeliek, stay at least 5 yards away from the Tank to avoid chaining [Holy Wrath].
Healers
Healers need to be assigned to starting at each of the four corners of the room, focusing on healing the tank in that position. Each time a Mark goes out, one healer in each position needs to rotate to the next position. Careful movements and paying attention is critical.