Izzet Spellementals is a red spell-slinging shell built around Eddymurk Crab and Hearth Elemental, making Flashfreeze a premium answer to their red threats like Slickshot Show-Off and Burst Lightning. Day of Black Sun, cast for a small X, sweeps their early creatures before they can chain spells into a bigger board. Sage of the Skies offers a cheap, resilient flying blocker/clock while you dig for sweepers. Consult the Star Charts and a Duress are too passive against a deck that wants to go over the top with spell-triggered growth, and the extra Deadly Cover-Up is too slow, so those come out.

Mono-Green Landfall is entirely green, so Flashfreeze counters almost anything they cast, including Earthbender Ascension and Mightform Harmonizer. Day of Black Sun is the key sweeper since it strips abilities before destroying, shutting off Mightform Harmonizer's landfall doubling and clearing their creatures in the same sweep. Thor, God of Thunder is a flier that dodges their ground-based creature mass and adds reach. Sear and Spell Snare are too slow one-for-one answers against a deck that goes wide, and Consult the Star Charts doesn't affect the board, so they're cut.

This is a control mirror decided by who resolves their card advantage engines and top-end threats first. Duress strips their Negate, Three Steps Ahead, or Day of Judgment before you commit a key spell, while Disdainful Stroke counters their Jeskai Revelation (MV7) or Thor, God of Thunder (MV5) outright. Bring in your own Thor, God of Thunder pair as a resilient flying win condition that also generates value off your graveyard. Nowhere to Run and Sear are removal aimed at creatures this matchup rarely presents, and Pest Control has almost no legal targets, so all three come out.