During research on the new zerg known as the Corruptor, the Vaul became interested in the concept of infested warships. Being one of the most powerful units in the Koprulu Sector, the infestation of Battlecruisers was very influential in deciding what to adapt into the Vaul arsenal. While infested, these ships became airborne turrets that could attack both ground and air forces alike before eventually dying. Although this comes at a cost of mobility, the lost of such a powerful unit can be crippling to Terran forces. As such, the Vaul began to use advanced Xel'Naga cybernetics and evolutionary technology to improve the Zerg's infestation technique. What developed became the first generation bioship in the Koprulu Sector outside the Zerg Broods.
Bio-cruisers appear as Battlecruisers hybridized with enlarged versions of other zerg breeds. Instead of metallic wings on the rear, these ships have two sets of Guardian "wings" to help maintain flight in or outside of planetary atmospheres and deep space. To move in hyperspace, the ships use the same method as Behemoths by tearing a rift in space. For weapons, Bio-cruisers use a system of Glaive Wurm launchers set around the same areas as laser batteries. On average, most ships have roughly eight sets of launchers with hundreds of wurms being grown in parts normally used as crew quarters. This gives the Bio-cruiser the same amount of firepower as a small swarm of Mutalisks, which is only the tip of the ship's full arsenal.
Besides Glaive Wurms, Bio-cruisers have their own version of the Yamato Cannon. The process first involves the development of Infested Terrans inside organic growth compartments. Second the infested units enter an area that forms an egg around each unit. The eggs are then filled with a substance that absorbs the force of large impacts to prevent premature detonation. Then eggs are moved into the neck area where hybrized Hydralisk muscles fire them a great speeds. Impact with the egg usually deals damage equal to a Terran Nuke. This is very effective in taking out tightly clustered units or buildings in one to two shots.
In the area formally used as a mess hall, some of the most highly corrosive acids are produced in a organ roughly resembling a stomach. Once full, Bio-cruisers expel the acid over a large area dissolving everything that comes in contact with it. This form of Acid Rain is highly effective in destroying large groups of ground infantry. Contact with the acid has a deleterious effect on buildings as well (Warcraft 3: Chimaera). Strong alloys of Neosteel are rendered weak as regular, non-zerg egg-shells making it easier for siege units to destroy them more efficiently.
Finally, Bio-cruisers can use their exterior glands to form a cocoon twice as strong as the ones used by Mutalisks. This gives the ship an extra layer of protection against enemy attacks while it recovers. In order to attack while cocooned, Bioships extend some of their glaive launchers outside the shell while it is forming. One downside to being cocooned is the loss of speed and maneuverability. Bio-cruisers usually move at a speed equal to a Dropship. While cocooned, the unit has the mobility of an Overlord before its speed evolution. Despite this, Bio-cruisers can take a pounding like an Ultralisk and still deal large amounts of destruction against enemy forces.
- Infested Cannon - each egg deals 500 explosive damage to both ground and air targets. Can get off two shots faster than a regular Battlecruiser
- Acid Rain - deals 250 damage to a large area on the ground. Corroded buildings take 20% extra damage from all enemy attacks
- Bio-Cocoon - unit receives +400 non-regenerative HPs, but loses 50% speed.