Starstones are special stones that always remember where they last were. They usually flash green, but some rarer ones are blue. A notable, blue-flashing starstone was owned by Lady Gisela and used in a hairpin to travel to (the new) Nightfall; another similar one travelLed to her bedroom, which was found at Cyrah's stall. They were both made by Cyrah Endal.
Starstones were used by the ancients to "teleport" from one place to another before light-leaping was discovered.