After scanning many galaxies, many stars, and many planets, you have arrived and found the perfect host to take over humanity. However, you are not the only one. Your probe must compete against others to release virus and take over your host.
Players take on the role of an alien species, controlling a probe that moves around a human's body and releases virus. But, the virus must overcome the body's natural defenses as well as competing for dominance with the other viruses.
Probes arrive in any of the six origin spaces and begin to take over the host's body. As the body's defenses break down, taking over becomes easier until it is taken over completely. The virus that takes over enough body parts, wins the game.
Players must manage a hand of cards, a board position with its virion pieces, and a probe that requires actions to use. Cards synergize well with each other when used in the right configuration and can allow a player to maximize advantages. Also, cards have a different effect when used against the body and when used against other viruses.