A letter tucked behind one of the tombs in the room with the secret entrance.
(Hopefully people knowing the secret entrance will use it right away, but those following after us would search the room for an entrance and find this note)
Greetings. I am Tor Hammerfist, from the first search party sent by Efram. I trust you are our backup, and well armed. The trick to proceeding further in the crypt is to spill a small amount of blood into the grate below the status of Pelor, then the middle tomb will be movable.
If you do not have a cleric with you, I’d suggest you get one as there is some serious evil afoot here. The contents of the murals in the next room are pretty disturbing. Even more disturbing is the fact that evil has settled in here long enough to decorate.
I shall attempt to mark the passages we take with smudges of soot on the nearby wall so that you can reach us and our quarry as efficiently as possible. Initial resistance seemed light (two hobgoblins and two goblins) but proved challenging for us regardless. We are currently recovering and will proceed as quickly as possible. I will ensure we remove this letter if we exit the crypt before you arrive, so if you’re reading this we are still inside.