Upon casting hellfire blitz, you assume a flaming spectral form until the end of your turn. You immediately move up to 40 feet in a straight line. You can move through spaces occupied by other creatures, but you must end your turn in an unoccupied space. This movement doesn’t provoke opportunity attacks. Each creature whose space you pass through takes 6d6 fire damage, or half as much damage with a successful Dexterity saving throw. You leave a 5-foot-wide line of hellfire burning behind you in your path.    This hellfire continues burning for a number of rounds equal to your spellcasting ability modifier. A creature that ends its turn in hellfire or passes through the line on its turn takes 1d6 fire damage, or half as much damage with a successful Dexterity saving throw. A creature can take this damage only once per turn.