1: Old skeleton of an elf and his ruined equipment
2: Room overrun with giant scorpions
3: Ruined smithy overrun with giant poisonous frogs. A warhammer +1 can be found by searching
4: Ambush
5: Ruins of the former barracks, now haunted by spirits
6: Spirit of Ferran Martinez
7: A stand full of magical weapons and armor: shield +1, longsword +1, mace +2, chainmail +1
Searching the elven skeleton in the gatehouse will reveal a crumbling parchment scroll with three very important words in elven. Translated they are Lux, Samosud, and Shestni. While in the keep, you will run into patrols of undead very often - if you speak the word Shestni to them they will let you pass.
When you get to the point marked 4 on the map, a large horde of 35 orcs and 15 hobgoblins raids the keep. The best way to defeat them is to approach from outside the central bastion and then fall back once they spring the ambush. Use sleep spells to keep them from all attacking you at once and to disable the archers. Using good tactics you should be able to handle the attack with 2nd level characters. If you wear them down enough they will start surrendering and you won’t have to battle them to the last survivor. On the body of one of the hobgoblins you will find journal entry 57.
In ruins of the barracks, you will run into the phantoms of the former defenders. Speak the word Lux and they will be dismissed from their undead existence, but not before they point out a floorboard where you can find journal entry 3 and some gems.
The spirit of Ferran Martinez will appear and wait for you to speak - saying the word Lux will get him to talk to you. He will ask you if the city has been freed, but if you lie to him he will be able to tell and will fade away. Telling him the truth will get him to relate the story of the Keep’s fall. As he mentions at the end, after he has faded away, you will have to use the Samosud password to get past the patrols to leave the Keep.