Galaxy Defenders: Extinction Protocol is the second campaign expansion for Galaxy Defenders, and can be used with or without Operation Strikeback.

In Extinction Protocol, the agents cross a portal to the invaders’ home planet, to fight the final battle against the Aliens - The adventure begins after the Agents defeat the Aliens on the Moon in Operation Strikeback.

Extinction Protocol adds many new features and new mechanics, introducing new aliens and new characters. Master Aliens, the highest-ranked invaders in the Alien Army are present in this set, including the Kingator - a giant creature, half reptile and half war-drone - and the Alien Queen, a nearly invincible opponent that can poison his victims before she finishes them with her dreadful claws.

The Agents can face these new enemies wearing lethal Power Armor, the ultimate mobile exoskeletons capable of imbuing the Agents with new unique powers and awesome firepower!

Agents are no longer alone in this war, as Extinction Protocol introduces a Non-Player Character (NPC) system, allowing intelligent non-player agents to fight side by side with the GD squad.