I'm running a semi-hard sci-fi campaign. Up until now, my

It's your setting OP, you decide what the rules are. Hell, if you make it weird and not what the players would expect in terms of how the world works, that might wind up as a good surprise.

Seriously though, what are your rules?

>>54277410

Haywire ancient death machines, forged by a species of long extinct aliens, they exist in many dimensions simultaneously and move in twisted, impossible ways.

>>54277410
>hard sci-fi
>galactic mercenaries and extradimensional beasts

Gee OP I dunno may just accept that you aren't doing hard scifi and then your life will be easier?

They could be different types of grey-goo scenarios gone wrong and grown to planetary size almost. Be it nano-machines, biological growths, etc.

>>54277477
>Seriously though, what are your rules?

Basically, I'm trying to keep everything as rooted in real science as I can. So far I've yet to pull an unspoken "because magic (science)" and I aim to keep it the way.

>>54277523
I'd prefer them be organic.

>>54277523
>semi-hard

>>54277778
>I'd prefer them be organic.
I don't think you know what the words 'eldritch horror' mean, senpai.

>>54277809
I'll admit I'm not well versed in the source material. Having said that they've always struck me as organic-ish.

>>54277707
Also, they're not extradimensional, just extragalactic.

>>54277410
You should check out Solaris, by Stanislaw Lem. It's about an incomprehensible alien horror but doesn't try to be magical or anything.

When in doubt, go All Tommorrows. Genetic manipulation.

>>54278100
Gave me the fucking shivers.

>>54277410

Answering this question depends entirely on how insecure you want to make your players. In general, you can categorize the degree you want to screw with them into three ranges: distant, imminent, and emergent.

A distant threat could be something far off but immensely, incomprehensibly powerful. These can be old, old, very fucking old post-singularity alien intelligences that have taken it upon themselves to turn suitable solar systems into dyson swarms to power a galactic cumputational network. For the most part they keep to themselves and are very far away - maybe the players encounter bracewell probes or scouting drones that have been drifting in the cold for millions of years until an onboard photometer detected enough light for it to activate and scout around. Make these threats formidable, lethal, but containable - but definitely telegraphing something else, something worse that might be coming.

And dead gods help them if a world they happen to be stuck on might be useful mass for a ringworld.

>>54278243

Imminent threats would be devastatingly powerful alien or post-human agents that have an agenda that directly or indirectly crosses paths with players, and for that matter, human polities. Imagine alien species which have been around for thousands of years, left all sorts of nightmarish toys like we leave behind coke bottles and land mines - and sometimes they come back to collect or analyze.

Major threats can be, again, autonomous or no-longer-dormant drones, but also prion weapon development facilities or lost cryo-prison colonies for psychotic extraterrestrials. They can be loosely comprehensible, but also have reasons to interact with humanity - in default ways which will not be fun for us.

File: biowar.jpg (27KB, 640x480px) Image search: [Google]

27KB, 640x480px

>>54277410
>>54277778
>>54277909
You may get organic extragalactic extradimensional organisms and hard sci-fi.

(Feral) biowars are Von Neumann machines based on organic materials and/or principles. For example, a laser cannon looks like a giant tree with leaves made of obsidian. This acts like an optical phased array. They breed by leaching materials from comets, asteroids and the like with bionanos.
http://www.orionsarm.com/eg-article/460db67bc3884
http://www.orionsarm.com/eg-article/48472ab83cce0

Their crew could look like not! Shadows from Babylon 5 which weave four-legged tanks from fullerene silk and omni-saliva. Explosive munitions and mines take the form of explosive crabs. Their viruses might modify the infected into extra computing nodes, eventually turning their calcium into an egg-like shell encasing only the vital organs.

Planetary crusts and biomes are converted into biogeominds.
http://www.orionsarm.com/eg-article/480a3f71b7738

A bio-dyson swarm is possible.
http://www.orionsarm.com/eg-article/48114a2e6b39a
This may be the goal your players have to prevent.

The extradimensional comes from their motherships being patterned after Dark Angels:
http://www.orionsarm.com/eg-article/480a48b000f5b

All sorts of raw materials and weapon systems encased within pocket universes, waiting for activation according to billion years old and possibly damaged protocols.
http://www.orionsarm.com/eg-article/4b53cbf383f6a

>>54278243
>>54278308

Emergent threats would be the really scary and unnerving phenomenae because they would be oft caused by humanity itself, existing in its space and enacting its own agendas. Think self-replicating nanoswarms that have taken up art projects, infrastructure AI's that create nearly-perfect digital replicas of people and sets them loose to see what would happen if their ethics were removed, or oligarchs so old and powerful that they no longer consider most humans as people they can so much as talk with.

>>54278243
>>54278308
>>54278334

With what I'm envisioning, a distant threat would be most appropriate. What I'm thinking is that the players are contracted by the CIA-like organization to retrieve a vessel carrying "tissue samples" that has been claimed by raiders outside of governed space. I feel like it'd be a good introduction to them.

An ancient race of very inhuman looking aliens united by a single creed. The Government was aware of their existence for a number of years now, but they seemed uninterested in human sectors so humans wisely stayed the fuck away.

These aliens are 3 legged pyramid-shaped be-tentacled things covered in layers of organic armor. Their technology is vaguely on level or slightly superior to humans, but individually they're many times stronger and more durable than a human. They possess almost no individual identity, and the gods they follow may be a lot more real than you'd expect.

What if you had guys who normally occupy different spatial dimensions and just kind of phase in for their scientists to run terrifying experiments on the 3d world. Also random ayylien hooligans might punch holes in 3d space or intentionally torment 3d life forms for amusement.