Ioun Stone, Emerald Shard

Wondrous Item, very rare, (requires attunement)

An irregularly shaped fragment of transluscent emerald that turns dull grey when its magic is expended. The emerald shard is subject to the normal rules of ioun stones. While active, the emerald shard absorbs 5 damage from every attack or damaging effect that hits the owner. The shard loses all its magical properties and ceases to function once it absorbs 120 damage.