Aliens: Phalanx is a 2020 novel written by Scott Sigler and published by Titan Books. On the planet Ataegina, humans live in a primitive, medieval society with no modern technology, hiding away in crumbling mountain strongholds from the Xenomorphs that roam the planet and kill or capture anyone caught out in the open. When these secure settlements begin mysteriously falling to the creatures, Liyah Cooper — an expert "runner" who routinely risks the dangers outside to ferry desperately needed supplies between holds — becomes determined to defeat the Xenomorphs and free Ataegina, before the demons claim all human life on the planet. It was released on February 25, 2020.
Swarms of lethal creatures with black husks, murderous claws, barbed tails and dreaded "tooth-tongues" rage across the land. Terrified survivors hide in ruined mountain keeps, where they eke out a meager existence. Skilled runners travel the treacherous paths between keeps, maintaining trade and sharing information. If caught, they die screaming.
Ahiliyah of Lemeth Hold is an exceptional runner, constantly risking her life for her people. When she and her closest companions discover a new weapon, it may offer one last chance to end the demon plague. But to save humanity, the trio must fight their way to the tunnels of Black Smoke Mountain – the lair of the mythical Demon Mother.
Liyah Cooper and her fellow runners Brandun and Creen successfully complete the return journey from Keflan to their home of Lemeth hold, avoiding the demons that prowl the open country hunting for victims. They bring with them medical supplies desperately needed to combat an outbreak of sickness in Lemeth, an ageing mountain fortress now maintained in a careful state of semi-decay so as not to attract the attention of the demons outside. Upon meeting with the Margrave, the hold's elected leader, Liyah is dismayed to learn that the disease has worsened in her absence, and much more medicine will be needed. With all of Lemeth's other runner teams either missing or already engaged on other runs, Liyah's team is to be sent back to Keflan mere days after returning, forgoing the customary period of rest. Despite her reservations, she accepts for the good of her people.
Liyah spends her brief period of respite catching up with those she holds dear, including her lover Tolio and the horribly disfigured General Sinesh Bishor, who received his injuries when he lost a great battle against the demons many years before. The two play war games, Liyah's determination to one day find a way to beat the demons countered by Sinesh's assertion that they cannot be overcome in combat. Liyah also takes part in mandatory combat training with several other civilian reserves, secretly dreaming of becoming one of Lemeth's warriors, but, as a woman, forbidden from joining their ranks. Later that day, the inhabitants of Lemeth witness the execution of another runner who refused to carry out her duties.
On their way to Keflan, Liyah, Brandun and Creen stop at Dakatera hold to trade supplies. Liyah meets with the Margravine, the only female leader in all of Ataegina, who offers her a new home in Dakatera and the opportunity to train the hold's runners, a position that would mean she never has to run herself again. Although tempted, Liyah respectfully declines. Her crew continues to Kelfan, narrowly escaping several demons that detect them outside. Entering the fortress, they find it has been completely overrun, its occupants either slaughtered, taken by the demons or deserted. Despite the danger, they find Keflan's store of medicine and take the entire supply, barely able to carry the weight. Sneaking out through a back entrance, they begin the arduous trek back to Lemeth. Nearing home, they are discovered and attacked by a demon — Liyah is barely able to kill it, in the process discovering that the caminus leaves they have woven into their clothing to help camouflage themselves serves to counteract the creature's acidic blood.
Arriving at back at Lemeth, Liyah learns that several hundred survivors from Keflan have reached other holds, but almost half of the fortress' population has been lost. In due course, many of these refugees arrive at Lemeth, but the Margrave is unsympathetic, blaming them for the loss of their hold and viewing them as nothing more than a burden on Lemeth. Worried for Creen's mental well-being following their ordeal, Liyah is able to convince the Margrave to relieve him of his running duties and instead let him research the effect of the caminus leaves on the demons. Shortly afterwards, Lemeth's senior runner returns from a trip to Jantal hold, barely alive, and reports that Jantal has fallen just like Keflan, before succumbing to her wounds. Liyah is named senior runner in her place, but her insistence that Lemeth's council need to act before a similar fate befalls them is ignored. Creen develops a paste from the caminus leaves that he believes will fatally clot demon blood, but the Margrave refuses to allow Liyah to conduct a trial. Undeterred, Liyah, Brandun and Creen sneak out to test the substance, and discover it is capable of killing a demon, although it takes a brief period of time to take effect.
Making their way back to Lemeth to report their findings, they encounter a large group of refugees fleeing from Dakatera, which has also been overrun. Liyah and Brandun help get them inside, the Margravine among them, although many are taken by the pursuing demons. Once inside, they are confronted by the furious Margrave of Lemeth, who berates Liyah for allowing even more refugees into the hold. A confrontation breaks out and Liyah is detained, but at that moment demons suddenly appear in the corridors, attacking the hold's occupants without warning. As Liyah attempts to reach the armory, the secret of the demons' new success is revealed — they have bred inside a species of burrowing animal native to Ataegina, and the resultant demons, adapted for tunnelling, have been digging into holds and allowing great hordes of demons inside unexpectedly.
Armed with Creen's new poison, Liyah leads a successful defence by forming defenders into a phalanx, creating a wall of shields that completely blocks the corridor and prevents the demons from flanking them, while stabbing at the creatures from within using spears tipped with Creen's poison. For the first time since they overran Ataegina many years before, the demons are routed. However, the damage to the hold is too severe to repair, and the survivors are left vulnerable to an expected second wave of creatures. Liyah leads her small force against this second wave on the fields outside Lemeth, forming her men into a circle, a phalanx with no end that cannot be flanked. The fighting is brutal, but the humans emerge victorious once again. In the aftermath, Liyah insists the survivors march on Black Smoke Mountain, home to the Demon Mother, and try to end the demon threat once and for all. She sends word to other surviving holds, requesting help and telling them how to make more of Creen's poison, before marching south.
Liyah and a force of several thousand elite warriors from Takanta meet up on the Boiling Plains near Black Smoke Mountain, where they are assaulted by a vast army of demons. Liyah once again forms a circular phalanx, but the Takantan commander insists on a standard linear formation, not wanting to diminish the impact of her expert archers. As a result, they are quickly flanked and decimated, and Liyah's remaining small force is overwhelmed and destroyed.
Liyah awakes cocooned in the demons' nest alongside Brandun, Creen and hundreds of others. All of the creature's victims are impregnated with Chestbursters, but Liyah, Brandun and Creen are saved by eating the caminus leaves on their camouflage clothing, which prevent the embryos developing, the tiny, malformed fetuses emerging from their mouths and dying on the floor. Escaping their cocoons, Liyah and her two companions encounter Zachariah, who takes them to his hideout. There he explains that he is a synthetic — something Liyah and her friends are unable to comprehend — who arrived on Ataegina over three hundred years previously when the colony ship Nan-Shan was infested with Xenomorphs and crashed on the planet. He goes on to tell the shocked and confused Lemethians that they are descended from the children who survived the crash, who escaped onto the surface with no modern technology and no adults to teach them of the wider universe. The Xenomorphs still aboard the Nan-Shan eventually reproduced in sufficient numbers to overwhelm the entire planet and force the survivors into their desperate existence hiding in secure holds.
Liyah convinces Zachariah to help them kill the Demon Mother, and they confront the monstrous creature in her chamber. Zachariah uses the Xenomorphs' indifference towards him to get close and redirect the geyser in the chamber, hoping to cook her alive — the blast of superheated water kills one of her protectors, but the Queen herself survives. A second protector kills Zachariah before Brandun leaps onto the Demon Mother, fighting his way through the protector and fatally stabbing the Queen with a final dose of poison, before she crushes him alive in her hands. The Demon Mother then sets off in pursuit of Liyah and Creen, but succumbs to the poison in her veins moments before she can kill them. The two survivors are subsequently found by another force of warriors from Vinden, along with survivors of the battle on the Boiling Planes, who have fought their way into the nest against little resistance, most of the demons having perished as a result of the poison used against them in the battle.
In due course the remaining Xenomorphs on Ataegina are mopped up and destroyed, and the people are once again free to live out in the open rather than cowering in mountain fortresses. Liyah becomes the ruler of a new, unified Ataegina, continuing to train her army against the threat of human raiders from across the sea to the north.
- The book's use of the plural Aliens in its title is notable, as every previous Alien novel published by Titan Books used the singular form of the franchise name (with the exception of Aliens: Bug Hunt, an anthology). Discounting Bug Hunt, Phalanx is the first novel to be published under the Aliens moniker since Aliens: No Exit some 12 years previous.
- At one point, the book states that Xenomorphs Drones have translucent teeth on their inner jaws. In every other appearance, these teeth are metallic and opaque like those in the creature's primary jaws. Only Queens have been shown to have clear teeth.
- After killing her first Xenomorph, Liyah puts on her backpack so that her crew can move out. Shortly after this, Brandun helps her put the pack on again.
- A large group of Keflanian arrive at Lemeth following the destruction of their hold. Earlier, the novel makes it clear the multitude of traps on the approach the the hold would make it impossible for anyone without intimate knowledge of their location to make it through. How then did the refugees get past them?
- The lab Creen takes over is said to be the hottest room in Lemeth, a fact attributed to its being situated deep beneath the settlement's ovens and kilns. However, heat rises, so it would likely be cooler below them, especially deep underground.
- Zachariah states he has been on Ataegina 319 years. Shortly afterwards, Creen incorrectly states it has been 318 years.