Max Rockfall inflicts damage and creates a sandstorm for 5 turns (8 if a Smooth Rock is held). Its power and whether it is a special or physical move depends on the move it is based on.
Gigantamax Drednaw slams its forelegs into the ground, causing a giant stone slab to rise from the ground. Drednaw then extends its neck and headbutts the slab, causing it to fall onto the opponent.
This article is part of Project Moves and Abilities, a Bulbapedia project that aims to write comprehensive articles on two related aspects of the Pokémon games.