8 cards where the set is “m21” and the card types include “dog”

Alpine Watchdog (Core Set 2021 #2)
Bolt Hound (Core Set 2021 #131)
Chandra's Magmutt (Core Set 2021 #137)
Igneous Cur (Core Set 2021 #153)
Pack Leader (Core Set 2021 #29)
Rambunctious Mutt (Core Set 2021 #30)
Rin and Seri, Inseparable (Core Set 2021 #278)
Selfless Savior (Core Set 2021 #36)

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