BGG buyers call it the easy first buy (6th player plus Reward deck). Its 20 aliens are rated outstanding with one dud, and the Reward module is widely considered the best.
Needs: Just the base game
Adds: 20 new aliens, an orange sixth player color, a Reward deck and the Cosmic Quakes rules.
Fixes: Fixes the five-player cap and gives winning encounters extra payoff.
BGG posters call it the most bang for the buck and a good sampler, and designer Jack Reda suggests only Odyssey unless you need more players; others note it costs as much as another game.
Needs: Just the base game
Adds: A campaign mode, 30 aliens plus 12 alternate-timeline aliens, Lux, Moons, Tech, Hazards, Rewards, Stations, Age/Evolution/Envoy cards and Team Cosmic rules.
Fixes: Packs most earlier expansion modules in one box, with many Green Alert aliens for newcomers.
SU&SD called it possibly the only true must-buy of the original five; BGG posters say it holds arguably the single best alien design of any expansion.
Needs: Just the base game
Adds: 30 new aliens, a 32-card Reward deck, four variants and ship markers.
Fixes: Adds the largest alien pool and a second Reward deck.
SU&SD found the Hazard deck too random for its reviewer but still ranks it third; Rob Burns says its aliens have one dud and Hazards are a good module; Messianic ranks it fourth of seven.
Needs: Just the base game
Adds: 20 new aliens, a black sixth/seventh player color, a Hazard deck and Cosmic Quakes.
Fixes: Adds a seventh player slot with Incursion and a random-hazard variant.
Nerdist says the Hidden Alliance dials almost solved the game's alliance dynamic; BGG calls it hit-and-miss with complex aliens, so best for experienced groups.
Needs: Just the base game
Adds: 30 new aliens, Hidden Alliance dials and essence cards.
Fixes: Reworks the alliance dynamic with hidden dial bids.
SU&SD calls it the easiest to skip, but BGG posters say it is the large-group expansion. Its Team Cosmic rules also appear in Odyssey, so it is only needed for 7-8 players.
Needs: Just the base game
Adds: 20 new aliens, a white player color, 7-8 player large-group cards and Team Cosmic rules.
Fixes: Lets big groups of 7-8 play the game.
BGG threads call it the weakest expansion by far, with mostly dud aliens; SU&SD still rated its space stations second in 2015, so it suits fans of that module only.
Needs: Just the base game
Adds: 25 new aliens and ten space station cards and tokens with the Space Station Conquest variant.
Fixes: Adds a map-like objective layer to the standard game.
Buy Cosmic Encounter base game:Amazon (opens in a new tab)Asmodee US (opens in a new tab)
Cosmic Incursion. BGG buyers' threads call it the easy first buy (6th player plus Reward deck) and Rob Burns rates its 20 aliens outstanding with one dud and its Reward module widely considered the best; SU&SD ranks it fourth in its 2015 order.
Our verdict: buy this first. It adds: 20 new aliens, an orange sixth player color, a Reward deck and the Cosmic Quakes rules.
We’d buy Cosmic Incursion first. See the side-by-side comparison for what each adds and needs.
Same publisher
Rankings are our editorial picks, built from the reviews linked on each expansion page. Last checked 2026-10-08.