Cathara's Rage (Keshanar)

Lightning bursts out in a 20-foot-radius Sphere centered on you. Other creatures in that area must succeed on a Dexterity saving throw, taking 6d8 Lightning damage on a failure or half as much damage on a successful one. Each creature must then succeed on a Strength saving throw or be pushed 5 feet directly away from you.

Using a Higher-level Spell Slot. The damage increases by 1d8 for each spell slot level above 4, and the distance it pushes creatures away from you increases by 5 feet.