Crystal Annihilation

The casting of Crystal Annihilation conjures giant crystal spikes to shoot up from the ground at violent speed.

The crystal spikes rip through the ground in a 500-foot-radius circle centered on that point, reaching upto 100 feet, and shakes creatures and structures in contact with the ground in that area.The ground in the area becomes difficult terrain. Each creature on the ground that is concentrating must make a Constitution saving throw. On a failed save, the creature's concentration is broken.

The spikes  deal 75  piercing damage to any structure in contact with the ground in the area when you cast the spell and at the start of each of your turns until the spell ends. If a structure drops to 0 hit points, it collapses and potentially damages nearby creatures. A creature within half the distance of a structure's height must make a Dexterity saving throw. On a failed save, the creature takes 5d6 bludgeoning damage, is knocked prone, and is buried in the rubble, requiring a DC 20 Strength (Athletics) check as an action to escape.

Crystal Annihilation is a siege spell, specifically designed to knock down battlements, walls, buildings, keeps, and barriers. The caster must choose whether to direct the giant piercing spikes that are erupting out of the ground or to allow the spell to work as it will. If the caster chooses to allow the spell to function autonomously they have no way to predict where a spike will erupt from. If the caster chooses to direct the spells destructive influence they can have 2 spikes shoot up per action till the end of the destruction. The spikes erupt from random angles and degrees and 1 spike per action can even erupt for another spike. Spikes can not erupt horizontally and may not have a bend or curve to them.

The GM can adjust the DC higher or lower, depending on the nature of the rubble. On a successful save, the creature takes half as much damage and doesn't fall prone or become buried.