Tesla - How much powder/slime and what colors? On the floor, or in the nearby cauldron?
Slisik - Jesme stands behind you looking at the pressure plate built into the floor. "I wonder how exactly this one works. Why do you think they built a magic door into this room?"
As you throw the rock into the air, the cauldron fires a bolt of flaming molten rock at the 'attack' incinerating it into the middle of the air. "WHOA!" In shock, she jumps back from the pressure plate she had been waiting on, only slightly, but the shift is enough for the door mechanism to release and shut behind you. The door locks with a heavy mechanical clank and Jesme's efforts to re-apply pressure to the plate fails.
After 10 seconds, the sound of steel on steel and concrete on concrete clanks in the room. Along the floor, a translucent slime rises from the cracks in the floor and starts to cover the surface of the room. The substance is surprisingly slick and very difficult to stand on. The floor begins to drop, with the edge facing the flaming pit going down.
It looks like the floor you're standing on is moving towards a 45 degree incline into the fiery pit. A greasy film is slowly covering the rap. The cauldron moves in sync with the floor, tilting by some unseen mechanism so that the boiling rock will eventually pour into the pit as well. Worst case scenerio, one might slip, fall into the flaming pit below, and then be coated in a torrent of molten rock. There is, however, time to react as the device moves incredibly slowly. You can here the muffled yells of Jesme on the other side of the door trying to explain the situation as she can see it.
"The door's stuck! The lizardfolk went in! I'm not sure what's happening."