Aven Eternal is a common Creature — Zombie Bird Warrior card from War of the Spark (WAR), collector number 42. Current market price: $0.24 (foil $0.38), TCGplayer market prices via Scryfall.
Flying When this creature enters, amass Zombies 1. (Put a +1/+1 counter on an Army you control. It's also a Zombie. If you don't control an Army, create a 0/0 black Zombie Army creature token first.)