The Nexus is a dungeon whose entrance is located in Borean Tundra in the World of Warcraft game. The level range for the normal dungeon is 68-73. The instance was released in the Wrath of the Lich King expansion. The dungeon contains 5 bosses. The end boss of The Nexus is Keristrasza.
Nestled at the bottom of the Nexus temple on Coldarra Island is the location for this five man dungeon. Above that is The Oculus which is a high level dungeon (70) and above that is an one dragon boss raid (The Eye of Eternity). Getting to the wrong one could kill you, however the Eye of Eternity does need to be started, it won't start just by entering the dungeon. Whilst its possible to go round the dungeon in a anti-clockwise direction, it generally recommended and what many people in fact do is to go clockwise. The last boss, Keristrasza must be defrosted before you can fight her.
The second boss changes according to which faction you are, i.e. whether you are Horde or Alliance. The female boss of the raid, Grand Magus Telestra, an image splitting mage wears a hat during the Winterveil festival so if you're after a hat, she's the one to go for. Nearly all the female bosses wear a hat during the Winterveil festival in December.
The first boss on the heroic version of the dungeon is dependant on whether you are Horde or Alliance. If you are Horde, you face Commander Stoutbeard, a dwarf warrior. For Alliance, its Commander Kolurg, an Orc warrior. The mechanics will be the same.
When you reach an area where people are frozen, you need to tread carefully that you don't inadvertently pull the boss. The boss will unfreeze itself when you approach it or use ranged to free. The Commander will come at you with adds so they need to be handled. Take out the adds first then the boss. The boss has a deadly whirlwind which is really the only thing you need to be worried about.
Grand Magus Telestra is a Blood Elf mage which you probably could tell by looking at it her and her name. This character is always a Belf Female and doesn't change depending on the faction you are fighting for.
If at Christmas, you are ever after a Christmas Hat, Telestra will be found wearing one and will drop when she's killed. Most female bosses and a few male bosses will drop the hat.
There's three main phases here, the first phase, you kill hit and avoid the damage. The second phase, Telestra will split into three bosses, one fire, one frost and another arcane. You need to kill all three bosses before she resumes as normal. Once she resumes, she'll throw you about it. When she's throwing you, you need your ranged to hit her. Once back on the ground, she'll repeat as a normal then split etc, etc.
Anomalus is a creature of pure energy. If you've done the Magisters Terrace on the Isle of Quel'Danas, you will have experienced a similar looking boss although the mechanics will be slightly different here.
During the fight, Anomalus will create sparks which you need to close quickly otherwise it will damage you through electricity. The tank should kite the boss down the ramp to the lower stage before attacking. The second phase, the boss will split into smaller rift creatures which you need to tank away from the boss and kill. When the mini-bosses have been killed, you can return to Anomalus and finish him off. How many rifts and splits he does depends on how long you take.
A word of warning before you start this boss, there is a patrol that walks round the boss so its advisable that you clear them without pulling the boss. If unsure, use a ranged character to pull and then the tank picks them up. Wait though for the patrol to be in between you and Ormorok and not with Ormorok between you and the patrol.
The main things you need to be worried about are his stomp and the ice mountains that he creates. So long as you can avoid both of these things, Ormorok won't be too much of a problem.
When you first reach the last zone where Keristrasza is being held, she will be sleeping in ice. You need to kill the dragonkin guard who walks round the dragon. Once the dragonkin is dead, you need to unfreeze her by clicking on the three crystal balls at various points in the room. When all three orbs have been deactivated, the fight will start and she'll approach one. As soon as it starts, the tank needs to pull the boss.
The most important thing to remember is to stay away from the front and to keep moving. If you stay too long, you'll be debuffed and movement will be slowed and damaged done to you will be increased. To break the debuff, you just need to move. If you can avoid being frozen on the ground then you wil get the achievement.