"Interrogate the Prisoner" Quest from Iron Tower

Hey everyone. I have done Iron Tower twice for the sake of quests, but I have a last quest that was started by an item dropped from Anoki’s corpse. Here’s the description:

According to this diary, Anoki was in the Iron Tower, hunting for the prisoner on orders from someone whom she only referred to as “the master”. It makes no mention of the prisoner’s name, but says Anoki discovered that the prisoner was being held at the top of the tower. She had, however, been unable to get past Desumo, a Priest of Mitra charged with guarding the way to the top because of his magic prowess.

She researched ways to circumvent his powerful attacks, and created Wardstones in various colors, which she hoped would aid in this endeavor. These stones Anoki gave to her “girls”, says the diary. Unfortunately it does not say how to use them.

Perhaps this Desumo character will let me pass, so that I may interrogate the prisoner. I am working for the Crown in this mission, after all. In any case, my first task should be to make my way to the very top of the tower, where Desmuo should be waiting. Hopefully, he won’t attack me on sight, but I’d better prepare myself.

I must be careful on my way up the tower. The diary makes mention of numerous traps and hardships on the way.

The quest says that “I should access the top floor”.

The thing is when I go to Iron tower, theren’s no quest marker (X) that signigies this quest should be done there. And as far as I know, the last floor is that golem boss fight and I don’t remember any NPCs there.

Since forming a 6 man group for this dungeon is a bit time-consuming, can you tell me what exactly should I be looking for?

Thanks in advance.

Kill the last boss. You should get a cut scene.