You place four crystals on the ground in an area within range that is no larger than a 10-foot-radius circle and imbue them with defensive magic. When you cast this spell, you designate any number of specific creatures or creature types to be ignored by the spell’s magic.

Until the spell ends, when a creature you didn’t designate comes within 30 feet of the crystals for the first time on a turn or ends its turn there, one crystal launches itself at the intruder. The creature must succeed on a DEX save or take 1d6 magical bludgeoning damage. Once a crystal has attacked a target in this way, it becomes nonmagical and falls to the ground at the target’s feet. Even if you can’t see the crystals, you immediately know when a crystal is triggered.

The spell ends when all the crystals have become nonmagical. If you cast this spell while a previous casting of circle of stones is still active, the crystals used in the first casting immediately become nonmagical, and the spell ends.