Chullan's Spell Mimic

When a creature casts a spell, you can attempt to store a copy of the spell in a Gem. If the creature is casting a spell of 3rd level or lower, you succeed to store a copy of the spell. If it is casting a spell of 4th level or higher, make an ability check using your spellcasting ability. The DC equals 10 + the spell's level. On a success, you succeed to store a copy of the spell. You can automatically succeed this check if you expend a spell slot equal to the level of the spell being cast up to 5th level. The gem breaks and loses its stored spell after 24 hours or when you cast this spell again