Watcher's Keep (Quest)

Watcher's Keep (Quest) is a side quest available Baldur's Gate II: Enhanced Edition and Baldur's Gate II: Throne of Bhaal.
The quest is a "side quest" because all content in Watcher's Keep is optional and not mandatory to complete the main story - however, this quest is mandatory if attempting to complete the Watcher's Keep storyline.
==Acquisition==
The quest is initially registered in the player's journal by engaging with the Odren, the leader of the Vigil Knight group at the exterior of Watcher's Keep.
==Journal entries==
===Registering the quest===
If the player agrees to assist the Vigil Knights with entering the keep and fixing the seals within to keep a "great evil" imprisoned, then the quest is registered into the journal, as follows:
:Journal entry: Watcher's Keep (accepts the quest)
:Brother Odren of the Knights of the Vigil has sent out a call for those capable of entering Watcher's Keep... an ancient prison holding a great evil imprisoned there by the god Helm himself. The evil is close to breaking the seals of its prison and becoming free. The Knights would enter the keep and perform a ritual to fix those seals, but cannot as they are too weak to bypass the traps and monsters within. I have accepted the task of entering the keep and fixing the seal that keeps this evil imprisoned. It may be a long task... the keep is large and quite dangerous... but Odren says there is still some time before the remaining seals are broken. It must be done, however, or this creature will be freed and endanger all.
If Gorion's Ward declines to help, then the Knights remain and can be spoken to at a later time, but there is no way for the party to enter Watcher's Keep until they agree to help the Knights. Declining the quest results in the following Journal Entry:
:Journal entry: Watcher's Keep (declines the quest)
:Brother Odren of the Knights of the Vigil has sent out a call for those capable of entering Watcher's Keep... an ancient prison holding a great evil imprisoned there by the god Helm himself. The evil is close to breaking the seals of its prison and becoming free. The Knights would enter the keep and perform a ritual to fix those seals, but cannot as they are too weak to bypass the traps and monsters within. I refused Odren's request to enter the keep and fix his problem, although he asked that I reconsider... if this evil escapes, he says, no one shall be safe. 
===Odren instructs the party===
The party is also instructed to get background information from Brother Pol and some necessary items before entry into the keep can be made. At this time another Journal entry update is registered:
:Journal entry: Watcher's Keep 
:Odren has brought me to the top of Watcher's Keep and shown me the entrance. To get inside, I will need the proper holy symbol and ritual from Brother Pol, who can also answer my questions. Equipment can be bought from Sister Garlena, who is giving us access to the Knights' resources.
The party will then make its way through the keep's various dungeon levels, one by one, until it finally gains access to the last level. There are no specific Journal entries registered for the "Watcher's Keep" questline of any consequence during the adventuring and exploration of these five levels, although there will be other side quests introduced, such as:
* Open the portal to the temple's lower levels
* Gather the four scepter keys
* The Gambling Cambion
* Unlocking the Final Seal
===After encountering the Imprisoned One===
===Completing the quest===