Your search for "Frontier Mastodon 663" revealed the following:
Frontier Mastodon (J22) from Jumpstart 2022, available at 401 Games Canada. Rarity: Common Finish: Normal Artist: Nils Hamm Card Text:Ferocious — Frontier Mastodon enters the battlefield with a +1/+1 counter on it if you control a creature with power 4...
Frontier Mastodon (FRF) from Fate Reforged, available at 401 Games Canada. Rarity: Common Finish: Normal Artist: Nils Hamm Card Text:Ferocious — Frontier Mastodon enters the battlefield with a +1/+1 counter on it if you control a creature with power 4...
Frontier Mastodon (Foil) (FRF) from Fate Reforged, available at 401 Games Canada. Rarity: Common Finish: Foil Artist: Nils Hamm Card Text:Ferocious — Frontier Mastodon enters the battlefield with a +1/+1 counter on it if you control a creature with power...
Frontier Mastodon - FRF Reprint (PLST) from The List, available at 401 Games Canada. Rarity: Common Finish: Normal Artist: Nils Hamm Card Text:Ferocious — Frontier Mastodon enters the battlefield with a +1/+1 counter on it if you control a creature...