Urog's Runic Lightning Rod

You place a small, spectral rune on a surface you can see within range. You may use an action to activate the rune. When the rune is activated, a stroke of lightning forms a 100-foot-long, 5-foot-wide Line targeted directly at you. Each creature in the Line between you and the placed rune makes a Dexterity saving throw, taking 8d8 Lightning damage on a failed save or half as much damage on a successful one.

Using a Higher-Level Spell Slot. The damage increases by 1d8 for each spell slot level above 5.