I went into the Copper Coronet, talked to the owner, got upstairs, found my way into a dungeon, and found a guy with a carrion crawler for a friend. He talks about 4 keys to unlock The One. I found three of the keys can't find fourth. Help me!

(Thanks in advance!)
SGTJ.

1) in the lovers statue
2) right after you enter there is a room with the jellys in it.
3) the kobolds has 1.
4) the old mans friend