I think you should put symbols on the cube-key, like numbers maybe, for added confusion over the combination lock. It will probably waste a few Communication-type spells.

Maybe the Devil that appears has the top-most number tatoo'd on his forehead.

Perhaps. How about this:

The cube is colored on opposite sides the same color, two sides yellow, two green, & two red. Red has the numbers 1 & 3 upon it, green the numbers 1 & 3, and yellow 2 & 2, put in such a way that no two similar numbers are touching one another. The slot below the inscription is painted yellow on the top and bottom, green at the back, and red on both the sides. Both the yellow areas in the indent are marked with 2's, but the green is marked with a 3, and both red areas are marked with 1's.

Sound about right?

You can't solve that puzzle if both Red's are numbered "1", you know that right?
It sounds a bit complicated if it doesn't actually do anything!

There's lots of stuff you can add to confuse the party, but at the end of the day you have a room that locks them in until they fight two Bearded Devils.
The rest is just fluff you can modify depending on what sort of dungeon/adventure you put the room in.

Is there anything that says the numbers have to match up? Misleading hints FTW.

Do I gotta be a member of this 'game' to participate?

No, but membership is free and comes with the added benefit of including the Workshop in your games subscriptions for easy notification of updates

Then sign me up, and I'll get to work on the room of roominess and roomitude. The room of ages... So roomie that it will blow your roomfilled minds.

So, like the opposite of a mindflayer?

The search for the jewel dove brought hopes and a renewed anticipation when the rogue Lydia entered through the dungeon corridor to find a chest in the middle of the room. Her search through this maze proved uneventful. Lydia was trying to make a name for herself. Ohhh...the cost the jeweled dove would prove on the closed ended blackmarket. 1000 maybe 2000gold pieces. Sure, it was greed that perpetuated her into the room. Sylvan the Half-Elf Fighter entered cautious that there were more denizens to encounter as he put a hand to Lydia warning her of the dangers these dungeons still presented. The human mage Alan conjured light for them to see in the room but not before, the cleric Elwind detect a faint presence of evil from within the chest in the middle of the floor.

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Hey guys, thought Id chime in and submit an entry for fun. This is a pretty cool thing to have. Good idea. I want to subscribe and let everyone know about my entry. Its not fancy but took several core elements and mixed and matched them with a monster encounter for what could be an enjoyable encounter. Real quick the Chest is surrounded by a camouflage pit trap. No reset, I guess nobody has made it this far into the dungeon. The chest is trapped with poison darts that fly out of the wall. Two ghouls one from the entrance to the room and the exit of the room are chasing the heroes as each hero try to fend off the assailants while Lydia retrieves whats in the chest. In the chest is what she is looking for but finds out that she has bitten off more than she can chew. She retrieves a cursed item of which she is afraid to lose the item and afraid of damaging it.

Dungeon Terrain-
Unworked Stone Wall /DC 15 Climb Check
Break DC 65 / Hardness 8 / 900hp
Ground: Dense Rubble / Difficult Terrain / 2squares to move
Height-40 feet Cavernous
Width-4ft x 5ft
Wooden Door : Entrance/Exit Hardness 5 / 2inches / 20hp
Break DC 20

Traps-
Bestow Curse Trap On Golden Dove With Jeweled Eyes
CR 4; automatic reset; spell effect(bestow curse,
5th level cleric, DC 14 Will Save Negates);
Search DC 28; Disable Device DC 28

Camouflaged Pit Trap: CR 1; Mechanical; location trigger;
no reset; DC 14 Reflex Save Avoids; 10 ft. deep( 1d6, fall)
Search DC 20; Disable Device 20

Poison Dart Trap : CR 1; mechanical; location trigger; manual reset;
Attack +8 ranged( 1d4 plus poison / fortiude save vs. DC 12; 1d4 Constitution Damage)

2 Ghouls
Ghoul
CR: 1
Initiative: +2
Speed: 30ft
AC: 14
BAB: +2 with chance of paralysis
Reach: 5ft
Specials: Ghoul Fever, Paralysis
Saves: Fort+0, Ref+2, Will+5

X: Ghouls
Square: Chest with Cursed Dove
Circle: camouflaged pit trap

Nice setup for the room and traps, SV. I like the fact that the big trap is at the end It could lead to a small arc