You create a space of pure energy in a 30-foot- radius, 300-foot-high cylinder centered on a point on the ground within range. Creatures in this area are knocked prone and cannot lose this condition while there. A creature that enters the area for the first time on a turn or starts its turn there is knocked prone and takes 4d6 bludgeoning damage. A flying creature in the area immediately falls to the ground and is knocked prone. A creature must succeed on a Strength saving throw to move or perform any action. Each foot of movement while in the area costs a creature 5 extra feet.   A prone creature that ends its turn in the cylinder must succeed on a Strength saving throw or be forced into the ground as the energy pulls it down. It is restrained and incapacitated by the crushing pressure and the ground around it, but it gains the benefits of three-quarters cover, as only the upper part of their body is visible. A creature can repeat the saving throw as an action on each of its turns, freeing itself from the ground on a success.   If the spell lasts for its full duration, the ground cracks under the tremendous weight generated and becomes difficult terrain. Each 5-foot-square area requires at least 1 minute to clear by hand to remove the difficult terrain.