The main campaign is focused on the Imperial Navy defending against Hive Fleet Leviathan. There is also a smaller additional campaign focused on the Flesh Tearers and a recently-added one focused on the Necrons. Main campaign screens show a star system with fleets that can be moved once each turn to position them to attack or defend a particular planet. Protected planets generate additional fleets. The number of fleets each side has during engagements determines how many points are given to it prior to the battle.
Prior to battles, a certain amount of points are allocated to each side, which can be spent to add ships to the player's fleet. These include frigates, light cruisers, cruisers, heavy cruisers, and battleships, or their equivalents for a particular faction (Tyranids don't have light or heavy cruisers). Some ships, like frigates, typically come in squadrons of at least 2. In campaigns, players can also assign certain cards for each ship or squadron that increase or grant a particular stat or ability. These are earned by completing primary and optional missions.
Skirmish and multiplayer modes are available for the following factions: Imperial Navy, Blood Angels, Hive Fleet Leviathan, Flesh Tearers, and Necrons. The two Space Marine factions (Blood Angels and Flesh Tearers) play (and even look) almost identical. Tyranids (Hive Fleet Leviathan) play very differently from others.
Most non-movement actions require a check to be passed first. This is done automatically, and the player sees dice appearing on the screen with the number and either a blue or red color on each, indicating a pass or a fail, respectively. Battles are fought on a relatively small rectangular 2D map that is either empty or has asteroid or ice fields in the way. Simple movement does not require any checks, but special movement actions, such as "Reload" or "Full Speed Ahead" do. Should the check fail, the player is no longer able to use leadership checks this turn. A player is given 3 leadership reroll chances per battle.
Imperial and Space Marine ships have Deflector Shields that must first be depleted before damage is applied to the armor. A strike on the shield generates an explosion that persists on the battlefield for several turns that affect the shields of any ship that adjoins it, as well as slowing down the movement of a ship through it. Explosions also have a chance of destroying any torpedo or small craft that runs into it. Tyranids use deflector spores instead of shields, so they react to explosions a little differently. Necrons have no shields, but all their ships have high armor ratings. During attacks, a defending ship is given a chance to buckle down. If the check succeeds, then the ship/squadron is given extra armor that may allow it to avoid damage even with shields down.
Boarding is also common and can be done either by ships in the immediate vicinity of one another or using teleportation (provided the target ship has its shields down or has no shields at all). Boarders attempt to damage the target ship or its systems. In case of direct boarding, if the attacking ship rolls a lower score than the defender, the attacker is the one that suffers damage (the game explains it as counter-boarding).
All ships are given the option to ram when using "Full Speed Ahead" and encountering an enemy ship. Ramming can do devastating damage, but also has a chance of damaging the ship doing the ramming. Imperials (with their prows) and Tyranids (with their claws and tentacles) excel at ramming.
Ships with 0 HP become hulks, drifting through the battlefield. They can either explode violently or will drift until they hit the edge of the map and warp out. Hulks can still be attacked, although they're typically worth more victory points as hulks than space dust.
If a ship needs to leave the battlefield, there are two options: reaching an edge of the battlefield or attempting to engage the warp drive. The former is done automatically, when a ship touches the edge, whether intentionally or accidentally. The latter requires a leadership check.
The game has examples of the following tropes:
- 100% Completion: Completing both primary and secondary objectives in campaign missions earns you cards that can be used on ships/squadrons in subsequent battles to boost their stats.
- 2-D Space: Justified, since it's based on a board game.
- Asteroid Thicket: Some maps might contain pockets of asteroids or ice that are dangerous to navigate. Attempting to move into or through such a thicket requires a check. A failed check results in heavy damage to the ship. On the upside, a ship within a thicket cannot be targeted, but also can't fire its weapons.
- Boarding Party: All ships can be used to attempt to board others.
- Direct boarding can be accomplished by getting very close to the target ship and selecting it for the boarding action. In this case, the player is shown the odds of success, based on the relative differences of the crew strengths. For example, a frigate may only have the boarding strength of 1, while a battleship might have 7. The final success is determined by a roll for each ship, added to the base value. Multiple ships can be used to attempt boarding of a single enemy vessel. In this case, their strength values are stacked, although they still only roll once. If the attackers succeed, then the defender is damaged/destroyed. If the defenders succeed, then the same happens to one of the attackers. If the final totals are tied, no ship sustains damage.
- Teleportation boarding can be accomplished for a close, but not necessarily touching, range during the final stage of a turn. This requires that the target ship either have no shields or that they be down at the moment. If the defender's roll fails, then the ship sustains damage, Since the teleportation is one-way, there is no way for the attacker to be damaged. Necrons use portals instead of teleporters, allowing them to attempt boarding multiple times per turn.
- Cosmetically Different Sides: The differences between the Blood Angels and the Flesh Tearers aren't very obvious, especially since both factions are using similar-looking ships of different shades of red and have the same weapons.
- Deflector Shields: Imperial and Space Marine ships are shielded. Frigates only get one shield point, while an Imperial battleship has four. All shield points must be down in order for enemy weapons (not counting torpedoes and small craft) to do damage. Shields must also be done on the target vessel for teleporters to be used for boarding. While Tyranid ships don't have shields, their defensive spores act in a very similar manner.
- Evil Versus Evil: The "Exterminatus" campaign has the Necrons facing off against the Tyranids. Even in a Grey-and-Gray Morality universe, this undoubtedly fits the trope.
- Hive Mind: Gameplay-wise, a Tyranid player can only control ships directly if there is a Hive ship in the vicinity. Said Hive ship must also pass a command check in order to be able to take direct control over a particular ship or squadron. If the check fails, then the ship/squadron will be autonomous for this turn. The player can also willingly forego an attempt to take control of a ship/squadron.
- Homing Projectile: Tyranids and Space Marines can fire guided torpedoes, which are piloted. Each turn, they can be given a new heading.
- Lightning Bruiser: Necrons. Their frigates are the fastest of all, and even their largest ships can fly clear across the battlefield, when using the "Full Speed Ahead" action. In addition, unlike every other faction, they can actually maneuver when using this action, frequently allowing their ships to circle around and come in from behind. In addition to speed, Necron ships are among the toughest, with even their frigates having lots of armor and plenty of deadly weapons.
- Living Ship: All Tyranid vessels are bioships. Outside of direct Hive Mind control, they act autonomously.
- Ramming Always Works: All ships are capable of ramming, provided they use the "Full Speed Ahead" action. Imperial ships have an advantage with their sharp prows, but a number of Tyranid ships are specially-grown with ramming in mind and might not have any other weapons at all.
- Space Fighter: Some ships are capable of launching small craft that can be used to intercept other small craft, torpedoes, or attack larger ships. Some are of the fighter type, while others are bombers.
- Sphere of Destruction: Some Necron ships can emit these, damaging any non-Necron ship in the area. Cruiser or battleship explosions can also produce these, dealing severe indiscriminate damage to any ship in the vicinity.
- Taking You with Me: Imperial and Necron ships being boarded by Tyranids have the option to engage their Self-Destruct Mechanism. If the leadership check passes, then the ship explodes, violently, dealing great damage to any ship in the vicinity. Space Marines are too proud to do that, though.
- Unfriendly Fire: It's not uncommon for one's own torpedoes to hit a friendly ship instead, especially since any torpedoes that don't impact a target continue traveling in a straight line. Averted with Tyranid torpedoes, which instinctively know not to hit other members of the hive. Also played straight with nova cannons, whose targeting reticle can drift from the original point.
- Wave-Motion Gun: Some Imperial cruisers and heavy cruisers have nova cannons. These long-range weapons can, potentially, do devastating damage to the enemy, but they're notoriously imprecise and have a minimum range.
