devil's foot prints

a flame appears at your feet if you are wearing shoes they will be torched your base movement increases by 10 as you sprint in a straight line of unoccupied space   aimed to an enemy thats within that line but needs to be farther then 20ft from you as you pass it , it needs to make a dexterity save or take 1d12 fire damage or half as much on a successful save the steps left behind will keep flickering dealing 1d4 to all in the path on that same turn .the burning footprints will stay for 3 rounds and to pass it another dex save is needed of 12.