Charlatan's Thunderous Thread*

You wrap a piece of thread around a creature or object no larger than medium size. For the duration of the spell, the caster can use an action to detonate the thread causing a thunder wave of electricity in a 30ft sphere around the threaded creature or object. Each creature within the detonation's range must make a dexterity saving throw. On a failed dexterity saving throw, the target takes [roll]2d6[/roll] lightning damage. On a successful, save the target takes half damage.