Enchant hellblaze

you touch one weapon, it begins to billow with black flames. 

on a successful hit with the enchanted weapon add 5d8 fire damage to the damage roll and the struck creature cannot regain hp for 1 hour. 

while the item is enchanted, the user can make a ranged attack with the enchantment with a range of 30 ft and your spellcasting modifier, on a hit it deals 5d8 fire damage and the creature cannot regain hp of 1 hour.

if the enchantment deals damage the spell ends, if the enchantment does not deal damage within 1 minute the spell also ends.

at higher levels: When cast using a spell slot above 6th level, the damage increases by 1d8 for each slot level above  6th.