Balefire

You evoke the merging of Poison and Fire to bring a painful demise to your foes. As an action you extend a hand and burning poison shoots forth in a 5ft wide 30ft long line. Creatures in this line must make a Dex save equal or higher than your spell save DC on a success they take half damage, any non-magical objects not being worn or carried automatically fail the save (unless they are adamantium in which case they are unaffected) and are runed and catch fire. The spell deals 1d8 Poison and Fire damage and creatures that failed the save catch fire for a number of rounds equal to the level the spell was cast. They take an additional 1d4 Poison and Fire damage and must spent their turn putting themselves out or continue to take damage until extinguished. Creatures who are resistant to only one of the damage types will still take the full damage dealt, they must be resistant to both types for the resistance to take effect. 

At Higher Levels: The number of d8's and d4's increases by 1 per spell slot expended above first. At level 2 it becomes 2d8 and 2d4, at level 3 it's 3d8 and 3d4, ect.