Sequids

The Sequids are a parasitic alien race defined by a single terrifying trait, the power to hijack the minds of other creatures. On their own they read as pink, squid-shaped things with three tentacles and bare, brain-like heads, drifting about aimless and submissive. Everything changes the instant one of them latches onto a living host. A lone Sequid taking a body is enough to link the entire swarm into one coordinated hive that thinks and strikes as a single will, shifting from scattered vermin into a focused force of ruthless conquerors.

Their strength lies less in the individual, which is fragile, than in sheer numbers and rapid reproduction. Bonded to a host, they suppress its autonomy completely and share sensory input across a sensitive psychic network, letting them register even the death of a single member. They also retain memory and tactical sense, recalling past foes like Invincible and playing a patient long game, though they tend to repeat the same schemes, which makes them predictable rather than adaptable.

Long before reaching Earth, the Sequids carved a path of ruin across the universe before crashing on Mars, where the shapeshifting Martians proved impossible to infect and instead kept the parasites as powerless slaves. Their fortunes turned when a crew of Earth astronauts arrived with Invincible watching over the mission for the Global Defense Agency. After a Martian secretly replaced astronaut Rus Livingston, the abandoned man became the host the Sequids needed, letting them unify, overthrow the Martians, and set course for Earth aboard a stolen ship.

The Guardians of the Globe, Atom Eve, and Invincible repelled that first assault, and Robot's cleansing device freed Rus, but a single Sequid stayed hidden in his body and seized him again once back on Earth. Following the Invincible War, the parasites bred in the sewers and burst into the city in force. This time the Guardians and the GDA answered with a containment barrier, curing disruptors, and teleport darts, yet the fight spiraled as the swarm smashed their equipment. Cornered with the barrier collapsing and no cure within reach, Invincible made the brutal choice to kill Rus and halt the spread, a decision that weighed heavily on everyone. A final lone Sequid later crawled out of Robot, only for Monster Girl to destroy it before it could take hold.

The Sequids have no true individuals of note, since their identity rests entirely in the collective, but several hosts stand out. Rus Livingston serves as their primary and most tragic vessel, seized and re-seized until his death ends the threat. During the Martian battle they also briefly commandeered Atom Eve and Robot before the Guardians pulled them free. Their possession fails against certain biologies, unable to pierce the near-invulnerable skin of Viltrumites or hold onto shapeshifting Martians. The concept draws on the Star Conquerors of DC Comics.