A seemingly normal clay pot that to the un-trained eye. For a scholar of nature, this is a deadly tool of wild fires.

This clay pot is filled with sicky tree snap and a mixture of extremely flammable crude oils as well as the spark of an unlit flame. This pot is then sealed tight letting in no air. when opened and exposed to the outside oxygen, the whole mixture combusts and propels the mixture out a great velocity. This is NOT a magical item, but very specifically a product of the scientific studies done in the city of Akros. 

Dragon's Breath: as an action, you can open the jar. The mixture trapped inside ejects out in a 20ft line. This effect targets one target (whichever creature or object that is within range and is closest to the source). That target is lit a flame as sticky, flaming sap sticks to their person and take 1d4 fire damage. At the beginning of each of their turns, the fire spreads and the number of d4's increase by 1 (ie. 2d4 on their first turn, 3d4 on their second turn) to a maximum of 6d4. This sap can not be extinguished by traditional means and will continue to burn until it has used up its fuel (determined by dm) or extinguished by magical means. Water has no effect on extinguishing the fame. Once this pot has been opened, it takes 10 minutes of uninterrupted repair to refill.