Now, Aribeth has left her diary in the room, read it to see what plagues the fallen heroine of Neverwinter to know that she’s forsaken her calling as a paladin. Unlock the door using the Portal Key you found in Aribeth’s room and enter the Host Tower. You’ll find the Teleporter in the middle of the room. This will help you access the levels of the Host Tower. There is a Floor Portal Stone for every level and you can find them across various levels, on bodies of fallen enemies et al. I really suggest going through this by level so it doesn’t get confusing as to what level you’ve already accessed or not.
At the Pinnacle, you’ll meet the former Head of the Arcane Brotherhood Arklem. He’s turned himself into a Lich now and seems to be trapped. He needs your help escaping but well, I’d rather you just kill him but you kinda need him to open the door. So free him and get him to open he door for you. Destroy the four braziers around the room and Arklem will free himself and open the door for you. Also, freeing Arklem will give you more insight into the world of Maugrim and the reasons for the plague.