Elemental Gem: Magic Eater

Elemental Gem: Magic Eater
Current Owner: n/a
Atop this silver ring is a tiny elemental gem which houses a powerful mote of elemental sentience, one which hungers for magic.
When the user succeeds on a saving throw or successfully is missed by an attack from a spell of 3rd level or lower, they may use their reaction to “eat” the spell and store it within the elemental gem, charging it. At any point while charged this way, the user may use their action to cast the spell from the ring using new targets, adhering to components the spell requires as normal. The spell uses the to-hit and spell save DC as determined by the original caster. The ring may only hold one spell.
Once the stored spell has been expended, the gem shatters, leaving the ring as a simple mundane item.