Missing sideboard cards? The full 14-card sideboard runs about $6.36.
Buy sideboard on ManapoolIzzet Spellementals wants to chain cheap spells like Opt, Sleight of Hand, and Prismari Charm to reduce the cost of Hearth Elemental and Eddymurk Crab, so Spell Pierce is excellent at taxing their early tempo plays or countering a key Traumatic Critique. Secret Identity and Shore Up protect your creatures from their bounce (Prismari Charm) and removal (Burst Lightning) while keeping the clock on. Since they have minimal creature-based removal, we trim the redundant Octopus Form copies and slower pump spells in favor of proactive protection and disruption.
Mono-Green Landfall grinds you out with Icetill Explorer, Mightform Harmonizer, and Earthbender Ascension scaling huge creatures, so Pyroclasm helps clean up their small early creatures like Llanowar Elves and Sazh's Chocobo before they snowball. Full Bore adds a pump option to push aggression. Soul-Guide Lantern is mostly a sideboard hedge against Esper Origins' flashback and graveyard shenanigans. Keep the low-impact pump spells trimmed since this matchup is more about racing than combat tricks.
Dimir Midrange leans on a heavy removal and disruption suite (Bitter Triumph, Requiting Hex, We Say Thee Nay!, Nowhere to Run) so protecting your threats matters more than pump spells that just get two-for-one'd. Secret Identity and Shore Up give your key creatures hexproof to dodge removal like Bitter Triumph and Requiting Hex, though note Nowhere to Run specifically lets them target your creatures as though they didn't have hexproof, so it still gets through. Spell Pierce punishes their proactive noncreature plays like Kaito, Bane of Nightmares. Cut the weaker pump effects that don't survive their removal-heavy game plan.