The Construct Quarter
Housing more bosses than any other, the Construct Quarter contains all kinds of bizarre experiments dreamt up by the Lich King's mad scientists. While Naxxramas was originally famed for the varied mechanics of its battles, the first construct boss, Patchwerk, was the exception to the rule and is the concept of a 'tank & spank' fight taken to the brutal extreme. Hitting both the tank and offtank devastatingly and relentlessly, healers are tasked with keeping both up in the face of Patchwerk's fearsome barrage of blows. Meanwhile, the raid's damage dealers must go all out with everything they have if they are to kill him within 6 minutes, at which point he enrages and becomes unstoppable. Relying less on execution or strategy than the other encounters, Patchwerk serves as the first real "gear check" of Naxxramas.
With him gone, there's a fun Frogger homage before you encounter Grobbulus, a strange, lumbering giant in the next room. Creating ever-increasing ripples of poison at his feet, Grobbulus must be moved all around the room if they are to be avoided. He also randomly injects players with venom, both poisoning them and causing them to spawn ripples of their own after a few seconds, thus reducing further the already limited amount of space available. Finally, he will create blobs of slime which must be tanked and killed. Not a particularly demanding fight, the main problem is the lack of space that ensues as it goes on, and the raid will likely find itself hemmed in with nowhere to run as the fight nears its end.
A quick jaunt up a ramp and through a sewer pipe and you'll arrive at Gluth, essentially a giant zombie dog, and one with quite the appetite. Possessing a vicious anti-healing debuff, you'll need two tanks to take turns on him while it wears off. Gluth also regularly frenzies, increasing both the speed and damage of his attacks, though this can be dispelled by certain classes. While all this goes on, numerous zombies are dumped into the room to feed him. Untankable and with too much health to be immediately killed, some lucky soul must kite them around for 90 seconds or so until Gluth uses his Decimate attack. This reduces the health of everything in the room to a quarter of its normal amount and sends the zombies running towards him. Any that reach Gluth are immediately eaten, with each one restoring 5 per cent of his health, so they must quickly be blasted down with all the area-of-effect (AoE) attacks the group has at its disposal.
With Gluth dead, the gate to his room is unlocked and the path is clear to the final encounter of the Construct Quarter - Thaddius. Blizzard's homage to the story of Frankenstein, Thaddius plays no part in the fight at first; instead he lies inert at the back of a huge chamber. Two guards, Feugen and Stalagg, stand watch on raised platforms on opposite sides of the room and it is them the raid must first deal with. Apart from regularly pulling the other's tank to them, they pose little real threat. However, they must die within seconds of each other before the next stage of the fight can start else the first to die will resurrect itself, putting things back to square one. Should you time it right, both of them die and the raid has a few seconds to leap across to Thaddius' platform for the second stage of the fight.
Tesla coils overload and Thaddius springs into life! After a few seconds of combat, he begins building up a large burst of electrical energy which polarizes everyone with either a positive or negative electrical charge. There are a few scant seconds for the players to sort themselves into + or - groups, apart from each other - if stood near players with the same polarity as you, your damage capabilities are multiplied, and this buff is essential as Thaddius has a huge amount of hit points to whittle down before he enrages. However, if players with opposite polarities stand too close to each other instead, sparks really will fly. To complicate matters further, he will continue to hit the group with the charges, sometimes changing their polarity and sometimes not, so players must be aware and ready to move again if necessary.
The Plague Quarter
The smallest wing of the four, the Plague Quarter has three bosses in fairly quick succession. The first of these, Noth the Plaguebringer, lies not far from the entrance and paces restlessly in his lair until the raid attack him. As the fight goes on, he calls upon the dead to rise up and assist him, so attention must be spread equally between attacking him and killing the spawns so the raid isn't overwhelmed. To make matters worse, Noth will randomly apply a curse to three members of the group which, if not removed within 10 seconds, will cause substantial damage to the entire group. He will also Blink away on occasion, resetting all threat and so putting any inattentive damage dealers at risk if they don't give the tank time on him again. Lastly, after 90 seconds of combat, Noth will teleport completely out of range and send more risen dead against the raid for a couple of minutes. Each time he does this, more and more skeletons will spawn so if he doesn't die before the third teleport, the raid runs the risk of being overrun completely.