17 cards where the text includes “mutate” and the color identity ≤ RUW

Archipelagore (Ikoria: Lair of Behemoths #41)
Cloudpiercer (Ikoria: Lair of Behemoths #112)
Cubwarden (Ikoria: Lair of Behemoths #7)
Dreamtail Heron (Ikoria: Lair of Behemoths #47)
Everquill Phoenix (March of the Machine Commander #275)
Huntmaster Liger (Ikoria: Lair of Behemoths #16)
Lore Drakkis (Ikoria: Lair of Behemoths #194)
Majestic Auricorn (Ikoria: Lair of Behemoths #22)
Mysterious Egg (Ikoria: Lair of Behemoths #3)
Pollywog Symbiote (Ikoria: Lair of Behemoths #63)
Porcuparrot (Ikoria: Lair of Behemoths #128)
Pouncing Shoreshark (Ikoria: Lair of Behemoths #64)
Regal Leosaur (Ikoria: Lair of Behemoths #202)
Sea-Dasher Octopus (Ikoria: Lair of Behemoths #66)
Souvenir Snatcher (Commander 2020 #38)
Vadrok, Apex of Thunder (Ikoria: Lair of Behemoths #214)
Vulpikeet (Ikoria: Lair of Behemoths #37)

In the blink of an eye, they strode from deep snow to the end of this search.