The loadstone is a fragment of a magnetic asteroid that was used as Greymung's footstool.
The lodestone came to the Wolfriders' attention when they took refuge in the troll caverns during the burning of the Holt. The magnetic lodestone attracted Skywise's metal cuffs. A curious Skywise is forced away, but Cutter uses the pommel of his sword, New Moon, to chip off a piece for Skywise
The star-gazer drills a hole in it and fashions a string made from the hair of his tribesmen, and has worn it as an amulet ever since.
He used the Lodestone to guide the Wolfriders across the desert after their escape from the troll caverns, and again to the Palace of the High Ones.