Domino Effect

Upon landing a critical hit upon a creature with a lower size category to you, you can knock it prone, along with any number of adjacent creatures of your choice with an equal lower lower size to the first creature. Chosen adjacent creatures can make a DC 15+your weapon modifier Dex save to avoid being knocked prone.

You can take this feat an additional time to repeat this effect using creatures adjacent to the first set of adjacent creatures. Double your weapon modifier added onto the DC of the first set of adjacent creatures.