Thalia's Persistent Ray

You summon the power of a comet and release it in a radiant beam in front of you in a line 150 feet long and 5 feet wide. Each creature in the line must make a Dexterity Saving throw taking 6d10 damage on a failed save and half as much on a success. The damage type is either fire, cold, or force.

On subsequent turns until the spell ends, you can use your action to continue firing. When you continue firing, you can choose to change the direction of the line by up to 45 degrees. While moving the beam in this way, it is only 60 feet long. All creatures the beam passes over in its movement must immediately make the saving throw, taking half damage on a failure and no damage on a success. If you move or take another action, the spell ends.