Cloud of Burning Ashes

You create a 20-foot-radius sphere of Ash centered on a point within range. The sphere spreads around corners, and its area is heavily obscured. It lasts for the duration or until a wind of moderate or greater speed (at least 10 miles per hour) disperses it. The Castor can use an action or bonus action to ignite the Ash cloud to deal 4d10 Fire Damage on a failed dexterity saving throw as well as knocked prone , half on a success  and they are instead pushed ten feet away from the center of the explosion, thus ending the spell  Other fire sources can ignite the Ash without the castor's action (eg Fireplace, Torches, Firebolt etc).

At Higher Levels. When you cast this spell using a spell slot of 5nd level or higher, the radius of the Ash increases by 5 feet for each slot level above 4st as well as a additional 1d10 fire Damage