On B2, while on your way to the yellow orb, you'll come across a room with some rock columns and a corpse with a scroll piece next to it. In the next room will be 2 goblins and a floor button. Instead of going there straight away, stay in the room with the corpse and move over to the 2 columns attached to each other in the right corner of the room. Attacking the columns will reveal that these 2 are actually made of ice and will shatter. Behind is a switch that will open a secret passage to a room where you can pick up a device called 'Sextant'.With this item, you can always transport yourself instantly to any teleportation room you have discovered so far from any location in the game!