Upon Entering the instance you will see Violet Hold Guards repelling streams of the blue dragonflight. To start the event talk to Lieutenant Sinclari who will kill all mobs in the room and then leave the instance will all the guards. The door to the isntance will be closed so be sure EVERYONE is inside before starting the encounter, and the door will be what the blue dragonflight is targeting similar to the dark portal in Black Morass. Portals will start spawning around the room - the portals can either spawn a melee eliete, a caster eliete, or a group of lesser elietes (2 melee 1 caster). On top of that the portal will also spawn waves of trash mobs until the main eliete(s) are dead, at which point the portal will close and another will spawn in a different location around the room.

There are crystals lying around the instance that when activated will stun all the mobs in the room as well as dealing damage - use these when you are overwhlemed with adds. Also note that all of the spawned mobs will try and destroy the front door of the instance - if the front door is destroyed then you "fail" the encounter and will need to reset the instance. After every 5 waves an untargetable blue dragonkin will release one of the 6 boss cages to start the boss encounter. This will happen for wave 6 and 12 - the final boss (wave 18) will always be Cyanigosa.

Videos of fighting through 5 portals: