30 cards where the mana value = 5 and the power = 7

Ayumi, the Last Visitor (Saviors of Kamigawa #122)
Blitz Hellion (Alara Reborn #49)
Bonded Herdbeast // Plated Kilnbeast (March of the Machine #178)
Bonded Herdbeast // Plated Kilnbeast (March of the Machine #178)
Changeling Titan (Lorwyn #200)
Crumbling Colossus (Magic 2012 #204)
Deity of Scars (Eventide #118)
Garruk's Gorehorn (Core Set 2021 #184)
Geralf's Masterpiece (Shadows over Innistrad #65)
Grizzled Outcasts // Krallenhorde Wantons (Innistrad #185)
Grizzled Outcasts // Krallenhorde Wantons (Innistrad #185)
Illusionary Wall (Masters Edition #39)
Lithophage (Duel Decks: Venser vs. Koth #57)
Maarika, Brutal Gladiator (Universes Within #15)
Morkrut Behemoth (Innistrad: Midnight Hunt #114)
Nyxborn Brute (Theros Beyond Death #144)
Phyrexian Hydra (Mirrodin Besieged #85)
Purphoros, Bronze-Blooded (Theros Beyond Death #150)
Scoria Wurm (Tenth Edition #227)
Shivan Wurm (Vintage Masters #261)
Sliver Legion (Time Spiral Remastered #261)
Sliver Overlord (Scourge #139)
Sliver Queen (Tempest Remastered #211)
Taniwha (Mirage #95)
The Balrog, Flame of Udûn (The Lord of the Rings: Tales of Middle-earth #297)
The First Sliver (Modern Horizons #200)
Thunderblust (Modern Masters 2015 #131)
Volrath, the Shapestealer (Commander 2019 #51)
Zalto, Fire Giant Duke (Adventures in the Forgotten Realms #171)
Zhur-Taa Ancient (Dragon's Maze #119)
Zilortha, Strength Incarnate (Commander Masters #366)
Zurgo Helmsmasher (Khans of Tarkir #214)

Though this query has ended, its relics still slumber in New Argive.