A Better Mouse trap?

[GutterFace]

So im designing some traps for a dungeon run for my PC's and i had an idea i need to get some feedback on

its the classic pit trap with a twist. the pit is 10 feet deep.
but inside the pit (i want it to take up 100% of the space in the pit) is a Gelatinous Cube.

say if a PC falls into the pit, failing his/her Ref save, i want; instead of falling damage, for the Cube to get an auto-engulf ability on them. seeing as the DC for the pit save is 16 and the engulf dc is a 13, would you have them roll twice, or if they don'e make the save DC for falling, automatically have the Cube get their engulf attack on them?

[Gorfnod]

This is actually quite commonly done and one of the better uses for a gelatinous cube. Players can't just kite the cube around when someone has already fallen in.

[Fouredged Sword]

Now, that isn't evil enough.

You have a 10ft pit that has a pressure plate on the bottom. The pressure plate triggers a hatch above the pit to drop a cube into the pit from above.

Worse, after the cube engulfs them, they notice it has also engulfed an anchor attached to a chain. The chain is hooked to a mechanism that lifts them and the cube back into the ceiling, closes the hatch, and resets the trap.

[Callin]

Oh and before that you could have a wall spring out and slam into them and on the wall is a Black Pudding! So fall into pit, Black Pudding Slam, Gelatinous Cube falls into pit, GC and PC rise back into hide away ceiling cubby resetting trap.

[GutterFace]

Now, that isn't evil enough.

You have a 10ft pit that has a pressure plate on the bottom. The pressure plate triggers a hatch above the pit to drop a cube into the pit from above.

Worse, after the cube engulfs them, they notice it has also engulfed an anchor attached to a chain. The chain is hooked to a mechanism that lifts them and the cube back into the ceiling, closes the hatch, and resets the trap.

BWAHAHAHA this is devious i love it. i might have to borrow this idea :)

[Psyren]

If you enter a square containing a cube you are automatically engulfed, so they would only get the pit save.

[Kaveman26]

Fill the bottom of the trap with flasks of oil and Grease the Walls. Have a tindertwig "triggered" as part of the trap "closing", falling damage+Instant BBQ