A simple trap. Step in the middle of it and go tumbling down a pit. Whoever made it has tried to hide it to make it less open.
Detect: Per-based Traps at -4.
Disarm: DX-based Traps at -2. This would mean somehow making the spot in the ground that triggers the trap more solid or able to hold more weight.
Circumvent: DX or Jumping.
Evade: Dodge at -1.
Effects: 1d+2 crushing from a 3-yard fall.
Notes: Tougher traps are wider (more victims fall in and harder to jump athwart), deeper (more damage), spiked (impaling damage), or harder to find or disable. Tweak as needed to kill more characters. For example, a pit with a 7-yard that is 3-yards wide deals 2d+2 crushing to up to 3 victims. A 10-yard fall does 3d crushing; a 13-yard fall does 3d+1 crushing; a 17-yard fall does 4d-1 crushing. And Wizards of the Coast shouldn't use this name for so many traps.