Ring, rare (requires attunement by a spellcaster)
This smooth ring of ebony has silver bands running along the outside. While wearing this this ring you have darkvision out to a range of 60 feet.
The ring has 5 charges. While holding it, you can use an action to expend 1 charge to cast the darkness spell from it, or 5 charges to summon a beast of terrifying ferocity. The creature immediately appears in an unoccupied piece of ground you can see within 30 feet and is friendly to you and your companions. It obeys any verbal commands that you issue to it (no action required by you). After 1 hour, the creature leaves.
The ring regains all charges at dawn.
-Mordenkainens Tome of Marvelous Magic II (edited)