66 FALSE DOOR TRAP. The portcullis near the door appears stuck in place about five feet off the floor. The door will open, but a clever spring-loaded spear trap will discharge when it does so, attacking as a fourth level fighter.
Furthermore, the portcullis will close immediately with a grinding shriek and a paralyzing gas (save versus paralyzation of suffer the effects for 3d4 turns) will be released, affecting the whole passage between the secret door and the portcullis.
Next the portcullis will raise to five feet again with another horrendous sound. Should the adventurers remain in the area, random encounters are twice as likely due to the recent noise. This trap will remain sprung for 1d12+12 hours, when the spear and gas assembly will spontaneously reset (it can do this about a dozen times before maintenance is required to keep the trap operational).