Start off by talking to Mr Ex, the guy who teleports you to all PvM places.
You will find all PvM places here.
General Graardor:
Click on General Graardor. You will be taken to the Killcount chamber. Get 40 killcount and head into the boss room.
Graardor fights with melee and ranged attacks, so make sure to bring hybrid armour.
K'ril Tsutsaroth:
Click on K'ril Tsutsaroth. You will be taken to the Killcount chamber. Get 40 killcount and head into the boss room.
K'ril fights with melee. He is one of the easiest bosses, and has a high respawn rate. Be careful!
Kree'arra:
Go to the second page of the dialogue, and you will see this page:
Click on Kree'arra. You will be taken to the Killcount chamber. Get 40 killcount and head into the boss room.
Kree'arra fights with ranged, and can only be attacked with ranged methods. Kree'arra is one of the hardest bosses.
Commander Zilyana:
Click on Commander Zilyana. You will be taken to the Killcount chamber. Get 40 killcount and head into the boss room.
Zilyana fights with melee and can hit quite a lot. Be careful!
Nex:
Click on Nex. You will be taken to Nex's bank room where you can get ready for the fight.
When you are ready to fight, you will be taken into Nex's room, where she will shout her allies' names.
Nex has five phases she goes through during the fight, so I will outline them all here. Nex will also use a power through all five phases. She dashes through one of the four sides, damaging and dragging any players caught.
Smoke Phase:
Nex attacks using ranged and melee abilities, and will often do an ability to make your character cough, which lowers stats. She also poisons.
After fighting her through these abilities, you will be given the chance to kill Fumus. Do so, and you will weaken Nex, forcing her to go onto her next phase, the Shadow Phase.
Shadow Phase:
Nex attacks using melee abilities, and an ability that has no element. This ability will make shadows appear on the floor, which, if stayed on, deal tons of damage to your character. She will also darken the room a lot.
After fighting her through these abilities, you will be given the chance to kill Umbra. Do so, and you will further weaken Nex, forcing her onto her next phase, the Blood Phase.
Blood Phase:
Nex attacks using magic and melee abilities, and also has new powers to boot. She will summon Blood Reavers, which must be killed otherwise she will steal health off of them. When Nex yells "A Siphon will solve this!", any damage you do to her will HEAL her instead of damage her. She will also siphon health off of any alive Blood Reavers.
Nex will also shout "I demand a blood sacrifice!" A player will be marked in red. This player must run out of range, or have damage dealt to them, and everybody's prayer points halved.
After fighting her through these abilities, you will be given the chance to kill Cruor. Do so, and you will further weaken Nex, forcing her onto her next phase, the Ice Phase.
Ice Phase:
Nex will attack using melee and magic. She will use no abilities, although she does use Ice Barrage for her magic. Keep fighting her, and you will be given the chance to kill Glacies. Do so, and you will weaken Nex to the max, enraging her. She will be forced onto her final phase, the Zaros Phase.
Zaros Phase:
(Excuse the Windows 8 Options ^_^)
Nex will turn on Soulsplit and use deflect melee, ranged and magic throughout the fight. These appear above Nex's head. Nex will also heal back to half health, forcing you to kill her even more. After you kill her, she will use Wrath. Run, and she will die.
Luckily, I got Pernix after the first kill!
CONGRATULATIONS, YOU HAVE DEFEATED NEX! Now go get some torva.
Disclaimer: Nex is very dangerous. It is not advised to solo her. I only managed it due to Godmode for this guide. Always go in a group you trust.