General Hint: The easiest way to get rid of your foes is to split their coterie and feed on the single target (it is not the way to enjoy the game but it helps in situations like this one). In order to split enemy's coterie you should use a single character of yours as a bait to lure one or a few bad guys. Sometimes it happens that they kill the bait but there's no need to worry about it! indeed they will return one per one to their original position.. I wouldn't be in the last one's shoes!
Of course you will be able to revive the bait with a scroll or a common discipline.
BTW Sir, which is the exact area in the monastery ?