Ahzidal's Inferno

You call upon either the spirit of a phoenix or the essence of hell depending on what material component you use for this spell (if you have a feature or magic item that allows you to ignore material components then you may freely choose between them). Upon making your decision, you mix this energy with your own magic and unleash it in a direct line 30 feet wide and 100 feet long. All creatures within this area must make a Dexterity save, taking 8d8 + 20 fire damage on failing and needing to roll an additional saving throw for you corresponding material component on a failure. On a success, they take half damage and do not need to make the second saving throw. Regardless of if any or all of the creatures make their saving throws, the land that was scorched by your spell is counted as difficult terrain, and any nonmagical items that aren't being worn or carried and can catch fire will catch fire. The land can be smoothed over with 5 minutes of work per 5 foot square.

Spirit of Phoenix: The victims of your spell must make a Charisma saving throw, any undead making the saving throw at disadvantage. On a failure, a creature takes 6d10 radiant damage and is blinded, undead taking double radiant damage. On a success, the creature takes half damage and is not blinded. A blinded creature may reroll the Charisma saving throw at the end of each of its rounds to end the blinded condition.

Essence of Phlegethos: The creatures caught in the second half of your spell must roll a Constitution saving throw, devils making the save at disadvantage. On a failure, a creature takes 6d10 necrotic damage and is stunned until the end of their next turn, devils taking the necrotic damage regardless of resistance or immunity. On a success, the creature takes half damage and is not stunned.