Corrosive Blade

You brandish the weapon used in the spell's casting and make a melee attack with it against one creature within 5 feet of you. On a hit, the target suffers the weapon attack's normal effects and then becomes corroded with acid until the start of your next turn. While corroded the target has its armor class reduced by 1.

This spell's damage increases when you reach certain levels. At 5th level, the melee attack deals an extra 1d8 acid damage to the target on a hit, and the corrosion last an extra round. The damage roll increase by 1d8 and the corrosion extends another round at 11th level (2d8 and 3 rounds) and again at 17th level (3d8 and 4 rounds).