Kahan knocks on the door. Two things happen at once. Tendrils of lightning-light electricity in pink and purple radiate out from his knock to the perimeter of the door, eerily reminiscent of the purple and pink lights you dealt with in the last test.
When this happens, the door opens inward of its own accord, allowing you to see within.
As the door is opening, the 10 foot square stone floor below your feet begins sinking. You have no idea how far it will go down or what perils might present themselves if you allow yourselves to go down with the floor.
Meanwhile, you can see into the room. The knock his caused a chain reaction that spreads around the interior room.
The room itself is 30'x30' square, with a 30 foot high domed ceiling. About 20 feet off the ground is a small ledge running around the interior of the room.
But it is what is at the far end of the room that really catches your attention. Two things hang in mid-air, surrounded by a purplish hue as though in suspended animation. The pinkish electric tendrils spread around the room, reach out, and the purplish glow that holds them in suspended animation dissipates.
The object on your left is a very large chest, easily larger than the size of a man. It falls about 3 feet to the ground and solidly lands without bouncing, as if full.
The thing on your right is much more ominous. It is the stuff of nightmares, something you have heard about before--sometimes called the Eye Tyrant or Beholder. It appears as a large orb, 6 feet in diameter, dominated by a central eye and a large toothy maw, has 10 smaller eyes on stalks sprouting from the top of the orb. It shakes back and forth for a moment as if to shrug off its long wait in suspended animation, and then its eyes turn on you. You become weak in the knees as you see the evil, intelligence, and belligerence conveyed by those eyes.
Meanwhile, the floor you are on is sinking, and if you don't jump into the room soon, you will find out what danger it takes you to.
OOC: FYI, I am using conversion stats from the 3rd edition for this beholder, so if you are relying on the relatively weak stats in the 2nd edition Monster Manual, you will very much underestimate your opponent.