Corrosive Bolt

You hurl a blob of acid at an enemy within range. Make a ranged spell attack. On a hit, the target takes 1d8 acid damage. Unless the target is wearing magical armour, the next attack made against the target, before the end of your next turn, has a +1 to hit, as the acid creates a temporary weak spot at the wound. 

This spell's damage increases by 1d8 and armour penalty increases by -1 when you reach 5th Level (2d8) and (-2), 11th Level (3d8) and (-3), and 17th Level (4d8) and (-4).