Walking Ballista [Double Masters] DP18 Set: Expedition: Base Set Type:

Set: Expedition: Base Set Type: Supporter Rarity: Uncommon

Set: Double Masters Type: Creature — Angel Rarity: Mythic Cost: {3}{W}{W} Flying

so this is one of several places where players can get a rare or mythic rare in a single Set Booster

Set: Wizards of the Coast: Black Star Promos Type: Stadium Rarity: Black Star Promo

Two-Headed Dragon can block an additional creature each combat

Walking Ballista [Double Masters] DP18 Set: Expedition: Base Set Type:Set: Double Masters Type: Artifact Creature Construct Rarity: Rare Cost: {X}{X} Walking Ballista enters the battlefield with X +1 +1 counters on it. {4}: Put a +1 +1 counter on Walking Ballista. Remove a +1 +1 counter from Walking Ballista: It deals 1 damage to any target.