Descend into the tunnels and see what lurks below.
- Turn around and head down the open trap door in the church's floor.
- Take the stairs down and go through the open door to the right at the base of the stairs.
- Follow the passage forward and continue toward the next doorway.
- Turn to the right in the next room and follow this next passage toward the Lost Sectors.
- This will lead you into the Lost Sector: Atrium.