Aperture Orb

Wondrous item, very rare

This fist-sized black sphere bears engravings of various planar conjunctions upon its glassy surface. You can throw the orb as an action up to 60 feet. The orb implodes upon impact and is destroyed, causing a 5-foot-radius portal to open to a random plane. Each creature within a 10-foot radius of where the orb landed must succeed on a DC 15 Dexterity saving throw or be pulled into the portal. Three Small, two Medium, or one Large creature can be pulled into the portal before it closes at the end of your turn.