This is the second of two events in the raid expedition "Rathe Council Chambers: Eriak's Downfall".
Fight Xadrith the Voice while following kyv emotes and killing off the ukun and ratuk adds (this is a must). Eriak Zek becomes active upon Xadrith's death. Kill him while dealing with the same adds you encountered in 'The Brothers Zek' event.
The event is triggered through dialogue, so you can set up in the room.
a ratuk mauler begins speaking the words to summon a duplicate of itself.
Xadrith the Voice has been slain by _____!
Eriak Zek attacks shortly thereafter.
a Rallosian lifetaker - none?
a Rallosian warmaster - none?
Eriak reaches for a potion from his belt.
Eriak drinks a potion of speed!
Eriak Zek has been slain by _____!
This completes the expedition and (if you also have "The Brothers Zek" kill and all Rathe-theme pre-requisites) allows you to request the "Rallos Returns" raid.