Witch Bolt
A beam of crackling energy lances toward a creature within range, forming a sustained arc of lightning between you and the target. Make a ranged spell attack against it. On a hit, the target takes 2d12 Lightning damage.
On each of your subsequent turns, you can take a Bonus Action to deal 1d12 Lightning damage to the target automatically, even if the first attack missed. The spell ends if the target is ever outside the spell's range or if it has Total Cover from you.
Using a Higher-Level Spell Slot. The initial damage increases by 1d12 for each spell slot level above 1.
Witch Bolt 5.5e 2024 vs. 5e 2014 edition differences
The 2024 version increases range to 60 feet, changes initial damage to 2d12 on a hit, allows a bonus action on subsequent turns to deal 1d12 damage regardless of initial attack hit, and clarifies the damage increase per spell slot level.