Walking Ballista is a rare Artifact Creature — Construct card from Final Fantasy Commander (FIC), collector number 371. Current market price: $5.38, TCGplayer market prices via Scryfall.
This creature enters with X +1/+1 counters on it. {4}: Put a +1/+1 counter on this creature. Remove a +1/+1 counter from this creature: It deals 1 damage to any target.