The Virus deck features units, structures, upgrades, and attachments. Unlike the other races, the Virus does not gather ambria or water. Instead, the resource that they must manage is Maggots, which are spawned each turn by the Stagnant Reservoir and Festering Corpses. All Virus units and upgrades require Maggots.
The main attacking unit for the Virus is the Mosquito. Instead of dealing damage directly, the Mosquito attaches one Carrier card to any unit that it attacks. Various upgrades can be researched to weaken Carrier units, such as Fatigue (which makes Carriers move slower) and Infection I (which kills Carriers that have 1 health). Later in the game, it is possible to infect enemy structures and resurrect dead units.
The other races each have tech options which are used specifically to combat the Virus. Lizards have the Resistance upgrades, Rats have the Cure ability, and Beetles have the Liquefy pheromone. The Virus can win by wiping out the enemy before they reach these options, or by taking control of the opponent's army and using it against them.
- To morph a Maggot into a Mosquito, place the new Mosquito card face-down underneath the Maggot, then engage both cards 1 turn.
- To start researching an upgrade, check the upgrade's cost and build time. Pay the cost by discarding the specified number of maggots, place the upgrade face-down underneath a Stagnant Reservoir or Festering Corpse, then engage both cards according to the upgrade's build time.
- To reanimate a suppressed unit, attach a Reanimated card to the desired unit, place both cards face-down underneath a Festering Corpse, then engage the stack 1 turn.