Source: Tasha's Cauldron of Everything

Wondrous item, rare (requires attunement by a sorcerer)

This flickering crystal holds the essence of an Outer Plane. As an action, you can attach the shard to a Tiny object (such as a weapon or a piece of jewelry) or detach it. It falls off if your attunement to it ends. You can use the shard as a spellcasting focus while you hold or wear it.

Roll a d4 and consult the Outer Essence Shards table to determine the shard's essence and property. When you use a Metamagic option on a spell while you are holding or wearing the shard, you can use that property.

Outer Essence Shards
d4	Property
1	Lawful. You can end one of the following conditions affecting yourself or one creature you can see within 30 feet of you: charmed, blinded, deafened, frightened, poisoned, or stunned.
2	Chaotic. Choose one creature who takes damage from the spell. That target has disadvantage on attack rolls and ability checks made before the start of your next turn.
3	Good. You or one creature of your choice that you can see within 30 feet of you gains 3d6 temporary hit points.
4	Evil. Choose one creature who takes damage from the spell. That target takes an extra 3d6 necrotic damage.