Weight Spike

You envelope your hand in a purple light and increase the pull of gravity on a creature you touch. Make a melee spell attack against the target. You have advantage on the attack roll if the target is wearing heavy armor or is a large or larger size. On a hit, the target takes 2d4 bludgeoning damage and its speed is reduced by 10 feet untill the start of it's next turn as it's own weight pulls on on it.

This spells damage increases by 2d4 when you reach 5th level (4d4), 11th level (6d4), and 17th level (8d4).