Terry's Punching Portal

You summon a 1 foot by 1 foot portal up to 60ft away in an unoccupied space you can see next to a creature, a shimmering hand similar to yours comes out of the portal and punches the creature. make a melee spell attack against the creature. On hit the creature takes 1d8 magical bludgeoning damage, and as a reaction you can take a small item that isn't being held or carried that is within 5 feet of the creature. On the roll of a Critical hit the target of this attack is knocked prone (this effect does not stack)

At higher levels this spell's damage increases by 1d8 when you reach 5th level(2d8), 11th level (3d8), and 17th level (4d8)