Annul counters Phyrexian Dreadnought itself since it is an artifact spell, giving a clean proactive answer that sidesteps their counterspell suite protecting the Dreadnought once it resolves. Diabolic Edict forces a sacrifice when they have nothing but the Dreadnought in play, bypassing the fact that it has no relevant protection from edict effects. Duress is weak here since the opponent's deck is almost entirely instants and sorceries they'll happily cast through discard, and the one-shot bounce from Chain of Vapor is too slow against a deck that just recasts its combo piece. Keep the full counterspell and cantrip suite intact to keep pace with their tempo plan, and prioritize using Annul and Edict proactively rather than waiting to see the Dreadnought resolve.