you need to look for a guard that's on one of the rooms, can't remember where but there's a guard/guardian (in a room with a library) who will give you the key then ask you to do battle with him after. try searching all the rooms.

For the Pass to advance from Wenekera Fort Inside to Rucell, the guard you need to find is in the very top left area of the map in the north east room of the set of four rooms.

how can i get inside the wenekera fort inside ?:P