Okay, so the fight starts off when you enter. Phase 1 begins once he's done chanting to his minions.
Phase 1 = protect from magic (soulsplit optional also optimal)
Deal damage to nex until she reaches 192K/200K hp and this time nex is invulnerable and you must dps the first minion down.
While damaging the minion nex will randomly warp you to her and also drop any protection prayers along with disable them for a short period of time.
Phase 2 starts when the 1st minion dies.
Phase 2 = protect from range ALWAYS
During phase 2 nex hits you relatively hard with ranged attacks, all while spawning black circles at your feet, that explode for 1-4k dmg after 3 seconds, to avoid that simply move.
After nex is down to 185k/200k hp she will become invulnerable again, and you must kill 2nd minion.
After you kill the 2nd minion phase 3 begins
Phase 3 = protect from mage (soulsplit optional also optimal)
At the start of this phase nex will start a blood siphon, healing any incoming damage 100% amount. Simply don't attack nex during the siphon to avoid healing her.
When nex says "I demand a blood sacrifice" over her head, you need to run away (also use surge to get the distance) otherwise nex hits you for 1-2k typeless dmg, and heals it.
After you get nex to 175/200k hp you must kill the 3rd minion.
After the 3rd minion is dead phase 4 begings
Phase 4 = protect from mage (soulsplit optional also optimal)
During phase 4 nex will freeze you and surround you with ice blocks. Just make sure you have anticipation on or ready to use the freedom ability, that way you won't take the 7k+ dmg while being in the ice, and if nobody is there to break you out, you'll want to not take that damage.
Once you get nex back down to 175k (because she heals after 3rd minion) she will become invulnerable and you will need to kill the last (4th) minion.
After the last minion dies, nex goes into phase 5, zaros phase, alternating between protect from melee, protect from range, and soulsplit. also nex goes back to full hp.
At this time you just dps nex down and claim your kill.https://www.youtube.com/watch?v=QTGOEYrP9BY