Darkness stirs on the rim. Survive flesh infestations, cultist attacks, shambling undead, blood rains, invisible hunters, and other sanity-shredding perils. Capture and study entities to harness the power of the void. Conduct psychic rituals and awaken an evil machine god.

RimWorld - Anomaly is a horror-themed expansion inspired by classics like Cabin in the Woods, The Thing, The Cthulhu mythos, Hellraiser, and many more.

Warning - spoilers below.

Your colonists accidentally awaken a dark monolith and provoke an insane machine-mind of unfathomable power. Its terrifying manifestations begin to haunt the world. Survive these strange happenings as you study the new phenomena and learn how to end the madness.

Horror stories of every kind
It’s not just about fighting monsters. It’s paranoia, war, infestation, and mystery.

• A psychically-invisible hunter of human souls screeches outside your walls, returning every night to capture a new victim. The proximity alarm goes off, but you can’t see the beast. Study samples of the creature to learn to detect it. Then, become the hunters and kill it where it lives.
  
• A massive flesh creature is growing across the landscape, consuming and covering the whole map with a quivering mass of meat. It defends itself with beasts and acid. Fight it to get samples of its nervous system, then study them until you can venture to its heart and kill it for good.
  
• A parasite has mind-controlled some of your colonists - but who? They pretend to be human as they work to infest others. Track evidence, imprison, interrogate, and medically test people to find out who is infested before it’s too late.
  
• Your colonists become obsessed with a beautiful golden cube, one by one. They build statues of the cube. They worship the cube. They love the cube.
  
• A pulsating obelisk appears. Its dark power is unknown - it may duplicate people, teleport them to an realm of infinite gray mazes, or violently mutate them with new fleshy appendages. Learn what it does and overload it.
  
• A corpse arrives that looks exactly like one of your colonists - and seems to follow them.
  
• And many more weird and horrifying events!

Horror combat
You’ll fight battles against squealing fleshbeasts, hordes of shambling undead, spherical death-machines, massive devouring water-beasts, lumpen imitations of human beings, and many more sanity-shredding perils. Use the monsters against your normal human and mechanoid foes where you can.

When a great hole opens in the ground, you must venture to the caverns below, kill the massive creature that lurks beneath, and escape before the collapse.

Capture and study dark entities in your facility
To defeat the monolith’s manifestations, you must gain their power. Build a grand containment facility so you can capture monsters, study them, and exploit them. Expand it with stronger walls, floors, and doors to keep them secure. Exploit your captives to use their power against your enemies - but don’t push them too far!

Harvest the new bioferrite resource from your menagerie to craft experimental serums, flamethrowers and hellcat rifles, flesh-mutating pulsers, insanity-inducing weapons, and other void-powered tools.

Fight the cultists who serve the machine-mind
Macabre cultists will come and perform their psychic rituals with suicidal commitment. Destroy them before they abduct your people, summon bloody beasts, or just drive you mad.

Use psychic rituals for your own purposes. Summon the massed dead, rain rage-filled blood, or steal the minds and health of your foes - if you’re willing.

Escalate the power of the monolith to access the void in the new endgame
In the end, the world will go insane. All will be in darkness as terror squirms in the shadows. Only then may you face the machine god and choose your fate.

This expansion includes a new album by Alistair Lindsay, composer of the RimWorld soundtrack.