Well, I did something about a chessboard...
Returning
Valiant Knights
And Crafty Mages
After nights
Side by side travel together
For two ages
Until at half past eight
RULES BREAK
They enter through a tunnel with Deeper Darkness and Solid Fog, arriving to a black landing where a small chessboard awaits them. Further ahead lies a gigantic chessboard, with a white landing opposite to where the PCs arrived.
A creature has to position itself on the position of a cleric (crafty mages) from the red side, and other on the position of the adjacent knight (valiant knights). White figures will represent them on the small chessboard. (note: a search check DC 30 on the small chessboard will reveal the tiles to be an illusion, beneath which hides a lit coal basin).
Progression has to abide by the rules of chess, with one adittional restriction, Knight and Cleric have to be on adjacent squares (side by side they travel together) after every move by both pieces.
If the middle of the chessboard (half past eight) is crossed by half of the playing pieces after two moves (two ages) by each piece, the creatures in the room are free to exit through an opening at the white side’s wall, which starts closing, and shuts at the count of 5.
Failing to follow the rules (includes touching the white landing before the moves are completed) causes 1 Con permanent drain to all creatures within the room and returns any creature in the room the red landing.
The chessboard dissappears in an antimagic field, a river of lava rund under it.
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Ask for clarifications if you need them. My players loved it.