Runaway Steam-Kin is a rare Creature — Elemental card from Guilds of Ravnica Promos (PGRN), collector number 115p. Current market price: $3.02 (foil $9.34), TCGplayer market prices via Scryfall.
Whenever you cast a red spell, if this creature has fewer than three +1/+1 counters on it, put a +1/+1 counter on this creature. Remove three +1/+1 counters from this creature: Add {R}{R}{R}.