This is a mirror match, so the priority is answering their Phyrexian Dreadnought without weakening your own protective shell. Essence Flare enchants their 12/12 and puts a -0/-1 counter on it each of their upkeeps, gradually wearing the trampler down while your core protective suite stays intact. Annul can counter their Dreadnought outright since it's an artifact spell, giving you a second angle to stop the turn-one kill before it lands. Powder Keg and Peek are cut as too slow or too low-impact against a deck racing to kill in two attacks, and Flash of Insight is trimmed since your draw engine is already dense enough without it. Keep the rest of your counterspells and interaction (Counterspell, Foil, Daze, Stifle, Misdirection, Vision Charm) intact, as protecting your own Dreadnought and disrupting theirs is still the core game plan.