District Mascot is a rare Creature — Dog Mount card from Aetherdrift Promos (PDFT), collector number 158p. Current market price: $0.41 (foil $0.83), TCGplayer market prices via Scryfall.
This creature enters with a +1/+1 counter on it. {1}{G}, Remove two +1/+1 counters from this creature: Destroy target artifact. Whenever this creature attacks while saddled, put a +1/+1 counter on it. Saddle 1