Capacitance

You charge yourself with electrical energy which is released upon contact with another creature.

When you initially cast the spell the damage it will deal is equal to 1d4 (roll the dice when the damage is dealt, not beforehand). For each round you maintain concentration on the spell the lightning damage it will deal when released increases by 1d4 up to a max of 6d4. To release the spell, make a melee attack against a creature. On a hit, you allow the energy to flow through your weapon, or touch, releasing it and dealing the damage as bonus lightning damage for the attack.

If a creature comes into contact with you (e.g. by hitting you with a melee attack) during the spells duration the energy is immediately released. The spell is immediately dispelled and the creature takes the damage you have charged up.

If you lose concentration on the spell the energy doesn't immediately dissipate. While the amount of damage charged up no longer increases, the damage you have charged up so far remains until the end of your next turn. During this time the bonus damage can still be dealt if you make a successful melee attack, or come in contact with another creature. If you have not released the energy by the end of your next turn however it discharges through you, meaning you will take any damage you have charged up.