You may cast a spell with mana value less than X from among them without paying its mana cost
Shield Sphere It might not look like much, but that sort of innocuous feel is exactly why it flies under the radar

1 Space Marine Devastator 1 Ultramarines Honour Guard 1 Vexilus Praetor 1 Zephyrim 1 Vanguard Suppressor 1 Belisarius Cawl 1 Company Commander 1 Epistolary Librarian 1 Inquisitor Eisenhorn 1 Neyam Shai Murad 1 The Golden Throne 1 Sanguinary Priest 1 Deny the Witch 1 Primaris Chaplain 1 Entrapment Maneuver 1 Utter End 1 Reconnaissance Mission 5 (13) 1 Marneus Calgar 1 Celestine, the Living Saint 1 Triumph of Saint Katherine 1 Sister of Silence 1 Primaris Eliminator 1 Birth of the Imperium 1 The Flesh Is Weak 1 Sister Repentia 1 Knight Paladin 1 Redemptor Dreadnought 1 Grey Knight Paragon 1 Thunderwolf Cavalry 1 Fell the Mighty 7 (4) 1 Exterminatus 1 Reaver Titan 1 Deploy to the Front 1 Hour of Reckoning Common (30) 1 Mind Stone 1 Arcane Signet 1 Commander's Sphere 1 Command Tower 1 Dismal Backwater 1 Evolving Wilds 1 Path of Ancestry 1 Scoured Barrens 1 Terramorphic Expanse 1 Tranquil Cove 5 Island 7 Swamp 8 Plains Uncommon (19) 1 And They Shall Know No Fear 1 Grey Knight Paragon 1 Space Marine Scout 1 Thunderwolf Cavalry 1 Sicarian Infiltrator 1 Sanguinary Priest 1 Deny the Witch 1 Primaris Chaplain 1 Swords to Plowshares 1 Reconnaissance Mission 1 Mortify 1 Skullclamp 1 Sol Ring 1 Talisman of Dominance 1 Talisman of Hierarchy 1 Talisman of Progress 1 Arcane Sanctum 1 Ash Barrens 1 Memorial to Glory Rare (49) 1 Celestine, the Living Saint 1 Defenders of Humanity 1 For the Emperor

Brawl Not Legal Vintage Not Legal Timeless Not Legal Commander Not Legal Pauper Not Legal Oathbreaker Not Legal Penny Not Legal Toolbox Notes and Rules Information for Standard Procedure: At the time of Unfinitys release, the following card sets are permitted in the Standard format: Innistrad: Midnight Hunt, Innistrad: Crimson Vow, Kamigawa: Neon Dynasty, Streets of New Capenna, and Dominaria United
I will note at the time of writing this the second print run appears to be unclear to me as to when, or if it has already happened