Alaric's Static Cage

A 10-foot-radius spherical cage of static energy surrounding a roiling ball of lightning springs into existence centered on a point you choose within range. This cage remains for the spell’s duration. The cage’s space is difficult terrain. Each Large or smaller creature in the cage when it appears must succeed on a Strength saving throw or take 2d4 bludgeoning damage and be pulled up to 10 ft. toward the center point of the sphere. When a creature attempts to physically cross the boundary of the cage, it must succeed on a Strength saving throw. On a failed save, the creature is pulled up to 10 ft. toward the center point of the sphere.

Once per turn when a creature within the cage takes damage or is hit by an attack, you can choose to cause a bolt of lightning to leap from the center of the cage toward that creature, dealing 2d4 lightning damage.

As a bonus action, you can move the center of the cage up to 15 ft. to a point you choose within range.

At Higher Levels. When you cast this spell using a spell slot of 5 level or higher, choose between the following: the damage increases by 1d4 for each slot level above 4, or the radius of the cage increases by 5 ft for each slot level above 4th.