Heart of the Mountain

A sparkling fiery ruby shaped like a small heart. This object, while held or carried by a creature, grants them a natural AC of 19. The creature does not benefit from their Dexterity bonus or armor for AC while this effect is active, but can still use shields. The Heart of the Mountain also grants temporary hit points equal to 5 x your Constitution modifier, which you regain after a short or long rest.

While attuned by a dwarf, the Heart of the Mountain exudes a glittering, ruddy light and a pulsing warmth, granting immunity to fire damage to the holder and resistance to fire damage to up to five other creatures within 15 ft.