Chain Spark

As part of the action used to cast this spell, you must choose a metallic melee weapon to be used as the instrument for casting, otherwise the spell fails. You aim your weapon at a target within range. Make a ranged spell attack against the target. On a success, the target takes 3d6 lightning damage. On a hit, roll a 1d2. On a 2, you may target another enemy creature within 10 feet of the original target and make an additional ranged spell attack. This chain continues endlessly until either the attack misses or the caster chooses not to chain the spell. 

At Higher Levels: When you cast this spell using a spell slot of 3rd level or higher, the damage increases by 1d6 for each slot level above 2nd.