Brandish Necrotic Flames

You bless a held weapon with Silverish-green flames of death. When you or another creature strikes with the weapon the flames jump too and sear away the life force of the target dealing 1d8. A creature must make a CON 10 saving throw on their turn to dispel the flames. 

every turn the spell is failed to dispel it attempts to jump to another target within 5 feet, on succeeding on a 15  or higher.