Bile launchers arrive periodically during the mission "Planetfall" at pre-set locations. The player must defend and secure the cannons throughout the mission; when all five are prepared, the mission either advances to the next objective, or ends, depending on the state of the Dominion forces on the map. The player cannot allow the Dominion to destroy three bile launchers or the mission is lost.
Upon finishing their mutation, the bile launchers will automatically attack the Drakken defense cannons and Augustgrad gates around the map. They will not attack other units, and go inactive once all the cannons and gates are destroyed. They produce creep and rapidly heal if damaged.
Zagara is able to build bile launchers in Co-op Missions. They are unlocked once Zagara reaches Level 5, and upgrades for them become available at the spawning pool at Level 13.
The bile launcher is a slow-attacking defensive structure that deals heavy splash damage to targets in a radius. Unlike other defensive turrets, its attack is activated as an ability the player must manually command. The bile launcher's attacks take a moment to land at the target point, so the player must "lead" their targets if they are moving when targeted. One commanded to bombard an area, bile launchers will continue to fire on the area until told to choose a new target or stop.