With Gothik's demise, just one obstacle remains between the raid and entry into the heart of Naxxramas - the Four Horsemen. Both acclaimed and reviled in their original incarnation for the degree of co-ordination, tactical expertise and class stacking required to defeat them, the Horsemen remain a tricky proposition even in this simplified form.
The Four are Sir Zeliek, Lady Blaumeux, Thane Korgazz and - substituting for absent former horseman Mograine - Stratholme's own Baron Rivendare. The former two can be tanked by anyone standing within 20 yards of them, while the latter two are tanked normally. Each horseman has a variety of unique attacks, but all have one thing in common: after a certain number of seconds, each will apply a damaging and stacking debuff named after themselves (for example, the Mark of Rivendare) on anyone within a large radius of them, and will continue to apply more until the damage it does becomes fatal. To cope with this, the simplest way is to just have your respective tanks trade places with each other so that the first set of marks fade while another set are applied from their new target. As each horseman reaches 50 per cent health, they will Shield Wall to reduce the amount of damage they take, and even if killed, their corpses will continue to apply marks to whoever is in range.
With all four quarters cleared, the platform above the entrance becomes active, and access to the heart of Naxxramas is available.
A large circular room with a mass of bones in its centre, the opposite side of Frostwyrm Lair features a doorway covered in ice. As the raid nears the centre, the bones begin to swirl and come together until the frostwyrm Sapphiron is formed. A blue dragon encountered by Arthas and Anub'arak as they journeyed through Northrend, the then-Death Knight was impressed with his foe and raised him from the dead to serve the Scourge.
A relatively straightforward battle, Sapphiron could nonetheless be the hardest encounter to be found in Naxxramas. Like many dragons, he has a highly damaging cleave that will easily kill any melee who stray too near his front, and a whip of his tail will send players flying across the room. Additionally, Sapphiron will cast a large blizzard to rain ice shards down on parts of the room, as well as a life-drain on a selected player which, if not dispelled, will quickly reduce their health while increasing his own. Despite these formidable abilities, it is his ever-present Frost Aura that presents the greatest danger to the raid, constantly dealing damage to everyone every few seconds throughout the fight and likely to tax your healers to the limit. Frost resistance gear, while not necessary, may be a great help to inexperienced or undergeared groups here.
After a minute or so of combat, Sapphiron will take flight and spit frost bolts at 2 to 3 players, each doing considerable damage to anyone nearby and encasing the target in a block of ice, immobilising them for as long as it lasts. He then takes a deep breath and unleashes a huge cloud of frost over the entire chamber that slowly falls to the ground, which will instantly kill anyone it touches. The only way for the players to save themselves is to rush to the ice blocks their team-mates are trapped in and hide behind them, out of line of sight from Sapphiron and the frost cloud. Once the cloud hits the ground, the ice blocks are destroyed, and Sapphiron flies back down to resume the fight. The pattern repeats until death, whereupon a member of the group can loot an item that will allow access to the Malygos encounter in Coldarra. Meanwhile, the barricade of ice over the door shatters and the path is cleared to...
Once a member of the Kirin Tor who became enamoured with the forbidden arts of Necromancy, Kel'Thuzad was lured to Northrend by the Lich King and went on to become perhaps the most notable and infamous of his subjects. He is untargetable at first, and calls upon the legions of the Scourge to aid him; a small army of walking dead, abominations and banshees appear to answer this call. After a few minutes with the raid under siege, their numbers begin to thin out and Kel'thuzad finally joins the fray.
His most common attack is a volley of frostbolts which will hit most - if not all - of the raid. Additionally, he casts a single, highly damaging frostbolt at the tank, and a frost blast at a player which encases them and anyone standing too close at the time in a block of ice for 4 seconds, and does a fatal amount of damage over that time if not healed through. Another spell at his disposal is Detonate Mana, which burns through a portion of a caster's mana and causes damage to anyone nearby at the end of it. Finally, he will target a player and create a shadowy fissure beneath them which quickly explodes and instantly kills anything within.
At around the 45 per cent mark, a desperate Kel'Thuzad implores the Lich King for assistance. Portals open around the chamber and two Guardians of Icecrown enter the battle. These must be picked up and offtanked as they have too much health to realistically kill, so the fight becomes a race to finish off Kel'Thuzad before his increasingly powerful Guardians become strong enough to kill your tanks. Once their master is defeated, the Guardians scramble for the nearby portals and leave. Naxxramas is yours!