Unstable Arkanite Cluster

Arkanite crystals are brittle red gems that are volatile when subjected to certain reagents. This cluster of arkanite is fused to a delicate glass vial of one such reagent. You can use an action to throw the cluster at a point you can see within 30 feet of you. When you do, the cluster and reagent vial shatter, resulting in an explosive reaction. Each creature within 20 feet of the point must make a DC 13 Dexterity saving throw, taking 4d6 piercing damage on a failed save, or half as much damage on a successful one.

Immediately following the reaction, a single red crystal grows from the point of impact. The crystal grows in a cylinder that is 20 feet tall with a 5-foot radius, centered on the point where the vial shattered. It has 20 hit points, AC 13, and resistance to all damage except thunder damage or damage from siege weapons. A creature in the area of the crystal when it appears is either pushed to the nearest unoccupied space within 5 feet of it or is lifted on top of the crystal (its choice). The crystal is transparent, but lightly obscures everything behind it. It remains for 1 hour or until it drops to 0 hit points. At the end of the duration, the crystal crumbles to dust and vanishes into smoke as it finishes its reactive process.