Lodestone

A lodestone is a waste product of krakens. It has properties that permit the settlement of Vesrah from sinking.

Description
Lodestones are large, gray, and roughly spherical with some variations. A single smaller dark green stone is embedded within each.

Lodestones are used by the Water Ashari of Vesrah. They implant them in a location called the Aerie, and they are needed to keep Vesrah from sinking. Their power wanes over time. They are magnetic and are "profoundly magical". Lodestones are naturally connected to magic, in a way comparable to the newer whitestone.

History
Vesrah relies heavily on the lodestones, and while keeping them from sinking is the primary use, the general magic they provide is important to the Water Ashari.

Keyleth's final test in her Aramente was to retrieve three lodestones from the Elemental Plane of Water, which is guarded by a fearsome kraken, without killing the kraken. She and Vox Machina were successful.

Other lodestones

 * Caleb Widogast at times references a lodestone, but he is likely referring to real-world lodestone, ie, naturally occurring magnetite. This lodestone is a component of the spell Disintegrate.