The Nexus (instance)

The Nexus is a level 71-73 wing of the Nexus dungeon hub in the Borean Tundra. The dungeon layout is very open. You can go into different "wings", but the final boss, Keristrasza, a captured red dragon, can only be freed from her ice prison when you kill the previous three bosses.

Geography
To get there, you need to ride to Amber Ledge in northwestern Borean Tundra. A dragon will then fly you over to Coldarra. The entrance to the dungeon is somewhat hidden at the bottom of the rifts in the middle of Coldarra. Just go down, and when you see the Arcane Serpents, you are there.

Dragonwrath, Tarecgosa's Rest
A special version of the Nexus exists for players on the quest to obtain Dragonwrath, Tarecgosa's Rest.

Dungeon Denizens

 * Ancients
 * Arcane elemental (one, Anomalus)
 * Blood elves
 * Blue dragonspawn
 * Blue drakes
 * Blue drakonids
 * Colossus (one, Ormorok the Tree-Shaper)
 * Darkhounds
 * Draenei
 * Dwarves
 * Forsaken
 * High elves
 * Humans
 * Lashers
 * Mana serpents
 * Arcane wraiths
 * Mana surges
 * Night elves
 * Orcs
 * Orchids
 * Red dragon (one, Keristrasza)
 * Sparks
 * Spiders (critters)
 * Treants
 * Trolls

Bosses

 * Heroic mode; Optional
 * (vs Alliance)
 * (vs Horde)
 * Heroic mode; Optional
 * (vs Alliance)
 * (vs Horde)
 * (vs Horde)

Alliance or Horde forces
Going straight to Grand Magus Telestra from the Entrance, you will come across a hallway of Alliance or Horde forces that have been frozen in place by the blue dragonflight. The forces you encounter will always be the opposite of the force you are allied with (Alliance will always find frozen Horde and vice versa).

Ormorok's Kin
Ormorok and his creations were probably captured and put into the Nexus to serve as one of the guards. They were subjected to massive amounts of Arcane energy. Over time, they corrupted. Now, they possibly serve Malygos and the Blue Dragonflight, whether they like it or not.

Rift Spawn
Rift Spawn consist of Arcane elementals that have emerged in The Nexus due to the intense energies being gathered. Anomalus leads them and currently, they are all out of control. The Blue Dragonflight is attempting to fight them back.