In Metal Slug Attack's event, this boss is fought at the last stage. It takes on the appearance of a floating multi-colored blob, moving slowly across the battlefield. Upon detecting enemies, it will shapeshift into various forms in order to attack the enemy depending on their distance from it.
Downpour prompts the Invader to shapeshift into a monolith or Giant Hunter Walker against close and distant enemies respectively. In its monolith form, it rapid-fires numerous hieroglyphs, and shoots out energy shards from its "mouth" in its Giant Hunter Walker form.
Gatekeeper prompts the Invader to shapeshift into a massive slug-like creature, before opening its chest to reveal numerous laser beams that quickly decimate any enemy they make contact with, possessing more range than Downpour.
ET A Omnis' attacks can also recover its health based on the damage it deals, and can also weaken enemy armor significantly to allow it and its allies' attacks to deal more damage.
- Its name is Latin for "and from everything", which references its ability to transform into other inhuman Invaders.