Floating Sphere of Annihilation

The walls of this room are inscribed with glowing runes. A 5-foot-diameter sphere of inky darkness hovers several feet above the floor.

An unusually large sphere of annihilation is magically suspended in place. When intelligent creatures approach within 30 feet of the sphere, the runes on the walls activate the sphere. Roll initiative. On initiative counts 15 and 5, the sphere moves 30 feet in a straight line towards the closest creature within 300 feet of the sphere’s starting position, stopping once it enters that creature’s space. The sphere destroys nonliving obstacles it passes through. If it moves into a creature’s space, that creature makes a Dexterity saving throw , taking 66 (12d10) force damage on a failure. A creature reduced to 0 hit points by this damage dies, its body and gear utterly obliterated. The sphere returns to its original position if there are no living creatures within 300 feet of its starting space.

Magical Effect. This is a magical effect created by necromancy magic. Casting dispel magic on one of the runes requires a spellcasting ability check and triggers a Success.

Runes. The walls, floor, and ceiling each bear one glowing rune. A creature that makes an Arcana check recognizes that the runes cause the sphere to move towards living creatures. There are six runes. If all six runes are destroyed, the sphere no longer moves on its own and can’t be moved in any way.

Sphere. A creature that makes an Arcana check identifies the sphere as a large sphere of annihilation and can recall details about this magic item. The sphere acts like other spheres of annihilation with regard to the destruction of matter and the effects of coming into contact with a planar portal. Unlike other, smaller spheres, its movement can’t be mentally controlled—only temporarily halted.