Nowhere to go after killing the boss in the Karui Fortress

Hi, I killed the boss and received a pantheon upgrade however after that I did not know where to go and ended up wandering around aimlessly searching for where to go next, after googling the issue I found a bug thread that had many players complaining about being stuck here too, apparently a portal is supposed to open up and take me somewhere but that hasn't appeared, I have tried re-logging many times and killing the boss many times however nothing happens,

any ideas?

there is no portal there, go north

There are two entrances/exits (one you used and one on the other side of the arena) that are supposed to be open when you kill the boss. Was it not the case? And if you mean going further, there also is the entrance to the Ridge when you go north, as Ludvator said.