2-level Evocation
You channel lightning energy into a creature. The energy is harmless to the creature, but escapes in dangerous bursts to other nearby creatures.
Every time that creature strikes another creature with a melee attack, a spell with a range of touch, is struck by another creature with a melee attack, or ends their turn while grappling or being grappled by another creature, they deal 1d6 Lightning damage to that creature.
Once this spell has discharged 6 times (dealing up to 6d6 damage), the spell ends.
At higher levels: The spell can discharge damage 2 additional times (dealing 2d6 more total damage) before the spell ends for each slot level above 2nd.