Arcane Blood Ring

This dark grey iron band has one  embedded  garnet. You can use an action to concentrate on the garnet gem. You take necrotic damage equal to your level times the spell slot level you want to regain, the expended spell slots level has to be equal to or less than half your level (rounded up), and none of the slots can be 6th level or higher. This damage cannot be reduced or avoided in any way. You can also use an action to concentrate on the garnet gem and take  the exact opposite effect, allowing you to instead expend spell slots to regain hit points your level times the spell slot level. The ring may be used to regain expended spell slots as much as half your current level, after which the ring regains use of this effect at dawn.