Elemental Essence Shard (Fire)

This crackling crystal contains the essence of an elemental 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.

When you use a Metamagic option on a spell while you are holding or wearing the shard, you can use the following property:

One target of the spell that you can see catches fire. The burning target takes 2d10 Fire damage at the start of its next turn, and then the flames go out.