[Radek]

First of all, you'd better get all three glowstones:
- The first one is given to you by Sarellia after asking "City" or "Lost City".
- The second one is in the wooden chest in the room with 2 wooden chests (one of them is on the floor, the second one is on a ledge near the ceiling). The room is before the carousel.
- The third one is in the chest in the room with 6 channels, where you were attacked by 3 sharks. The room is after the carousel.
At any rate, you will need two glowstones for getting the last tablet.

Now, the tablets:
- The first one is in the chest in the hall with the Oracle.
- The second one is in a room, which can be reached from the hall with "cages" containing Cage Crabs. One of the cages has a broken floor. Swim down, kill the Cage Crab there and then swim up through a narrow passage in the ceiling above the crab.
- The third one is at the end of the city part starting behind the north exit from the carousel. You will need two glowstones there. You must put both glowstones in the receptacles, which open the doors to the levers, and then turn the levers. Otherwise, the levers will not move (more precisely, they will move but then they will return to the original positions immediately).