Spark stone

A spark stone is a magical item that, when crushed, grants its user a permanent boon of +1d6 fire damage on unarmed strikes (including attacks in wild shape) after being activated. Before being crushed, the spark stone appears as a spherical black rock shot through with fiery red lightning-like veins.

History
Keyleth was given the spark stone by Cerkonos following her successful Aramente trial at Pyrah. He told her that spark stones are found within the Elemental Plane of Fire, though they are rare, and that she could use it herself or give it to an ally.

Keyleth crushed the stone during Vox Machina's fight against a behir near Whitestone.