This from the TOTLM walkthrough
here.
10 - Having opened all six doors at area #9, you'll be able to enter the last door, which leads into this final resting place for the Watchknights. If you want, you can loot the four tombs in the room to find some magical weapons and armor. Unfortunately, the items not all that special (Mace +1, Spear +1, etc), but you can sell them if nothing else. The idea behind this room is to put the Watchknights to rest, which is accomplished by placing each knight's "Tale" (these Tales are found in the lower levels of each tower) in the appropriate tomb. Starting with the northwest tomb and moving clockwise, you need to place the following in each tomb: the Tale of Sir Serris, the Tale of Geddian, the Tale of Zierrki, and the Tale of Giles. As you place each parchment into the correct tomb, it will disappear and the knight's spirit will appear to thank you. Once all four knights have been put to rest, you will gain 420,000 experience and will be able to access Castle Maluradek through the front door back in the courtyard."