Shadowfell Shard

(requires attunement by a sorcerer)
•As an action, you can attach the shard to a Tiny object or detach it. 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 momentarily curse one creature targeted by the spell; choose one ability score, and until the end of your next turn, the the creature has disadvantage on ability checks and saving throws that use that ability.