Originally Posted by
MaxWilson
Me. I said the Barbarian could even Ready a Shove (Attack action) to shove the armor off the stairs every time it climbs back up.
I have never seen a DM rule that grapples cannot be readied--that ruling would make Mobile Earth Elementals extremely strong. Nor does the Ready action forbid you from Readying an Attack (Shove) in the first place, so forbidding it would actually be incorrect by RAW as well.