"Conquer the aegan islands" quest ?

I really need a little dominance to unlock my 4th hero now and there is a quest that gives 50 but I dont understand it.

It says Conquer the aegan islands and i have like 90% completed. I have unlocked the 500 dominance island group. what am I missing? or am i even able to do this quest without unlocking any other areas?

You need to conquer every one of the islands from the NPC.  Then the quest completes.