Sewer water pours into the room.
Type: mechanical / magical; Perception DC 22 (mechanical) / DC 34 (magical); Disable Device DC 32 (mechanical) / DC 34 (magical)
Trigger touch; Reset repair (mechanical) / none (magical)
When an attempt is made to open the door, the room fills up with sewer water at the rate of 1 ft. per round. After 10 rounds, the room is completely filled to its 10 ft. height. A DC 10 Swim check is required each round to stay afloat; once the room fills up, all characters are subject to drowning.
Since the party knows that the Order of the Staff is coming, the PCs can use the sewer strife trap against their foes if they are helping the Banlan Brotherhood.
If the adventurers decide to help the Order of the Staff, they can disarm the trap or otherwise warn the mages (who proceed into the room unheeded if not alerted to the danger).