If you have followed the quest chain to free mortai, you get a quest from the queen to kill rebel elves. This quest has you exi south from selvana tower, then head east into some caves. Head further east inside the caves to reach the elf stronghold
I have no quest to free "Mortai" (I guess you mean Morati, the dark elf from the beginning?). I didn't even know there's a quest involving her, since it has never been hinted to me.
