Ring of Fanged Familiars (Patreon)

Ring, uncommon

While wearing this fanged ring, you can use an action to cast the find familiar spell from it. When you do, the familiar takes the form of either a bat or rat (your choice each time), and it appears with 6 temporary hit points. The familiar is undead, instead of its normal type, and can take the Attack action on each of its turns. Whenever the familiar takes the Bite action, it has advantage on the attack roll, and on a hit, it deals an extra 1d6 necrotic damage to the target. You and the familiar then gain a number of temporary hit points equal to the necrotic damage dealt.

The familiar and temporary hit points disappear after 1 hour, or early if the familiar is reduced to 0 hit points or if you remove the ring. Once the ring has been used to cast the spell, it can't do so again until the next dusk.

"Does this look infected to you?"