Arcanaphage Stone 2014
Wondrous Item, rare, (requires attunement)
Similar to the rocks found in a bird's gizzard, this smooth stone helps an Arcanaphage (see Creature Codex) digest magic. While you hold or wear the stone, you have advantage on saving throws against spells.
Source: Vault of Magic (Kobold Press) · License: OPEN GAME LICENSE Version 1.0a details