The Cosmic Citizenship Council has declared it will allow two new alien species to join its ranks, but they forgot to make two copies of the filing form — which means that only one species can join! Now, the two candidates must fight for control of the planets to determine who deserves the right to become a Certified Civilization.

Cosmic Encounter Duel is a competitive standalone 2 player game in the Cosmic Encounter universe in which you and your closest frenemy race to be the one to control 5 planets. Each of 27 alien species comes equipped with its own different abilities that play with the game mechanisms in some way, giving you an edge in the fight, e.g., the Cheater, who can hold back an additional tactic that they can put toward any fight in the game — as long as the other player doesn't call out how they're trying to "cheat". How your game of Cosmic Encounter Duel pans out will inevitably be affected by which powers each dueling species has and how they play off of each other.

In addition to your special species and its ability, you have 20 spaceships to traverse the cosmos and keep control over the 5 planets you need to become a Certified Civilization. If you have a ship on a planet, you have control of it, even if your opponent also has ships there and you have to share control. You can deploy these ships to battle in duels, use them to act as reinforcements, or draw back for a retreat. Just don't lose them to the Warp or let them be claimed by the black void between the stars and get lost in space forever!

To play, players draw and solve Destiny cards, which come in 3 types: Discovery cards, Event cards, and Refresh cards. Discovery cards have you and your opponent discover a planet and battle for control, while Event cards ask you both to test your determination against a variety of challenges and cosmic calamities, and Refresh cards offer a respite in which you can recover ships, gather allies, and ultimately prepare for another clash.

At the start of a battle, you and your opponent secretly decide how many ships to send to the planet, and once they have been deployed, you can call upon any befriended envoys. To plan your attack, you secretly pick a card from your hand and a standing tactic from your collection to either guard your ships or blow your opponent's ships, then you duel, sending ships to face-off for control of the planet until the winner claims their prize while the loser retreats. After you and your opponent solve a Destiny card, you check the icon on the bottom of the card to choose which deck to draw from next, then the race continues.