- "But it ain't just that. Why does your pal need a pal? I figure the Engineer's come here to get some job done. And he needs a friend active to take care of unfinished business. Business like the pesky human vermin he's seen around this place."
- ―Galgo Helder referring to the two Engineers
The entity only referred to as the Second Engineer by Galgo Helder, was an Engineer awoken from stasis on the moon LV-223 by the Life and Death Engineer and was assigned to hunt down and kill the marines, as well as all other remaining life, present on the moon.
After the Life and Death Engineer landed on LV-223 (with the marines on the ship), it sets out to an Engineer temple. The marines quickly leave the ship and explore the terrain far away from the Engineer.
It reaches the temple and enters the interior. Inside it is a sarcophagus-like object. He opens it and wakes up another Engineer in stasis. The Engineer woke up the second one to kill all marines that had boarded it's ship.
The second Engineer waits outside as the first comes outside with two ampules of Chemical A0-3959X.91 – 15. The two are being observed by Galgo, who leaves to warn the marines, who had recently teamed up with Angela's group.
As the second Engineer patrols the jungle, he is suddenly ambushed by Galgo and Ahab, although initially getting the upper hand, the second eventually manages to overpower the two, forcing them to retreat and hide as the Engineer torches the jungle with his weapon and passes.
He later returns when the marines of the Hasdrubal land a dropship on the moon to rescue the recently captured Chris Hanlock, who was taken by Xenomorphs to be impregnated with a Queen. As Galgo and Ahab observe from a distance, looking to hijack the ship after the marines dispersed. Their plan fails as the Engineer detonates the ship and walks off to find the marines.
The Engineer finally finds the marines, who had only just recently quelled a Xenomorph attack and attacks them, now armed with dual-wield rifles. The marines fight back but to no success, numerous are killed, their numbers dwindling.
As the Engineer slowly makes his way into the entrance of the nest, the hive's Queen erupts from the ground and attacks it. The Engineer puts up a tremendous fight but is eventually caught off guard and impaled through the stomach by the Queen's tail, killing him.