23 cards where the color identity is GRU and the card types include “legendary”

Animar, Soul of Elements (Double Masters 2022 #171)
Averna, the Chaos Bloom (Commander Legends #269)
Beluna Grandsquall // Seek Thrills (Wilds of Eldraine #220)
Borborygmos and Fblthp (March of the Machine #219)
Gimbal, Gremlin Prodigy (March of the Machine Commander #3)
Illuna, Apex of Wishes (Dominaria United Commander #154)
Intet, the Dreamer (Double Masters 2022 #229)
Kalamax, the Stormsire (Commander 2020 #9)
Lara Croft, Tomb Raider (Secret Lair Drop #1501)
Loot, the Key to Everything (The Big Score #21)
Maelstrom Wanderer (Commander Masters #344)
Magus Lucea Kane (Warhammer 40,000 Commander #7)
Me, the Immortal (Doctor Who #147)
Miirym, Sentinel Wyrm (Commander Legends: Battle for Baldur's Gate #284)
Omnath, Locus of the Roil (Core Set 2020 #216)
Rashmi and Ragavan (March of the Machine Commander #8)
Riku of Many Paths (Outlaws of Thunder Junction #227)
Riku of Two Reflections (Double Masters #214)
Sarkhan Unbroken (Dragons of Tarkir #230)
Surrak Dragonclaw (Dominaria United Commander #169)
The Swarmlord (Warhammer 40,000 Commander #4)
Xyris, the Writhing Storm (Dominaria United Commander #175)
Yasova Dragonclaw (Fate Reforged #148)

This search is finished. Now the real work can begin.