Porting stones

Porting stones are stone discs that are used for teleportation. They can be controlled by the voice, and are used on Dragon Isle. A side effect is nausea and dizziness.

Quote from Flight to Dragon Isle
"Unfortunately for Root, the denizens of the vast fortress moved about by using porting stones - discs carved with runes and imbued with sorcery that could whisk you from one point to another. Root hated the porting stones: they made him sick."