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My question is whether or not the Inperium has the ability to terraform celestial bodies? Or is this something that would be deemed too dangerous if a technology to have? And if they do have it, why do they not use it to salvage dead worlds?

Honestly I think more often than not the Imperium terraforms worlds in the opposite direction through overpopulation and turning something once habitable into a toxic hellscape.

Off the top of my head I think the mechanicus can embark on terraforming activities, but I can't think of where I get that idea from.

They do. It takes a long time.

However, some dead worlds are also:

+ Unstable due to the core of the planet being cracked by orbital bombardment.

+ Infested by aliens such as Tyranids or Necrons after the bulk of their forces have already left. Would need to clear them out first before the planet can be reclaimed.

+ Touched by Chaos, which was why Exterminatus was called in the first place.

Yep. The mechanicus has terraforming tech. It's not quick, and the machines seem to be big enough to be a pretty large investment, but they can do it. They also have weather control devices that can in terraforming as well as agriculture.

The issue with salvaging dead worlds is that...
A.) The world has to be safe enough for them to set up these big, presumably expensive machines that won't produce a return on investment for a very long time.

B.) The world might be so "used up" that it's simply not worth reviving. If the imperium's main interest in a planet was the ore they could mine from it, then the imperium doesn't have much motivation to make the place livable after they've mined all the ore. If an ag-world has had the nutrients in its soil so completely used up that it's no longer cost-effective to restore the soil, then the planet is probably no longer suited to be an agworld.

Lots of planets are also ina constant state of terraforming - so say hiveworlds where the environment has collapsed and only terraforming gear is able to create oxygen etc.

"Belisarius Cawl: The Great Work" has Cawl terraforming Sotha to undo the effects of the Tyranid Invasion, as a favor to the Scythes of the Emperor.

DeathKorp_Rider wrote:
And if they do have it, why do they not use it to salvage dead worlds?

They do. Its very expensive and takes a long time. It's why Exterminatus is not invoked lightly. Even though you can salvage a dead planet, it is a process that takes centuries or millennia.

So it's something that happens in the background, and you're going to focus your limited resources on what has the biggest return for the shortest time. A recently exterminated planet can be terraformed, but you've probably got a few marginally habitable worlds that would be much easier to make fully habitable with the limited resources.

Better to get a half dozen planets with small weak biospheres to a fully productive state than try to fully restart a dead world. You can always come back later and fix the dead planet after you've helped a bunch of only half dead planets.

The other angle is if the Imperium actually cares about the world to bother. They can Terraform, but they can also build sealed Hive Cities and many worlds that they operate on have toxic atmospheres. They can genetically tinker with things and have a vast bloated population to work with.

So they can terraform some worlds; others they will just invest in with cities and environmental suits and import air, paid for by mineral and manufacture on a world where they have zero concern about clean air or pollution.

It could be supply and demand.

Agriworlds are of course an essential part of The Imperium, as they’re bread baskets for not just their solar system, but the wider sector etc.

Warp Travel isn’t entirely reliable, so having a certain ratio of such worlds in each sector or system seems desirable enough.

Perhaps you’ve found a dead but otherwise earth like planet in the Goldilocks zone, or perhaps a surfeit of moons in the Goldilocks zone orbiting a planet otherwise inimitable to life.

Those could both be candidates for terraforming, at least to the degree they can support nutrient rich crops, or even hardy fauna. Because nobody ever said the food being exported has to be tasty…

We also need to consider that whilst terraforming isn’t an instant thing? The Imperium very likely works on timescales we don’t really think of, and yes that may depend upon what exactly it is they need, and how essential it is.

Having an agriworld in each solar system sounds great, but if you’ve a nearby system with stable warp routes with multiple agriworlds or at least worlds capable of sustaining the ingredients of nutrient paste? Each system having its own local source is less important.

We also need to keep in mind Imperial Technology is not homogenous, even where you have a local or at least local-ish Forgeworld, because not all Forgeworlds produce all technologies. So whilst you may have a wealth of terraforming candidates? You may simply lack access, or at least ready access, to the necessary technology to do so. And being the well known bureaucratic nightmare, you’re far from guaranteed of being able to requisition it. There’s even a chance that should you get it, it could be reallocated before it’s completed it’s job, or simply breakdown beyond repair.

With the Imperium chances are getting the paperwork signed to approve the Terraformer takes longer than the Terraforming itself

Opposite Question: Can the Imperium basically "Tyranid" a world? Can they suck up every possible atom of usable material/biomass?

Dead Space calls it "planet Cracking" but it's done mostly with asteroids and large bits of mass. There has to be a way the Imperium harvests dead worlds for minerals and matter...

FezzikDaBullgryn wrote:
Opposite Question: Can the Imperium basically "Tyranid" a world? Can they suck up every possible atom of usable material/biomass?

Dead Space calls it "planet Cracking" but it's done mostly with asteroids and large bits of mass. There has to be a way the Imperium harvests dead worlds for minerals and matter...

Possibly? However, remember gravity and that could be locally effected, with unintended consequences.

Which in turn posits a Real World physics question. If you mined away half a planet, exporting the goodies away, the planet’s mass if course reduced. How drastically might that effect a solar system’s procession of the planets?

FezzikDaBullgryn wrote:
Opposite Question: Can the Imperium basically "Tyranid" a world? Can they suck up every possible atom of usable material/biomass?

Dead Space calls it "planet Cracking" but it's done mostly with asteroids and large bits of mass. There has to be a way the Imperium harvests dead worlds for minerals and matter...

Earth or Terra is basically there already. Mined out and 100% reliant on importing all it requires.

The big difference is the Tyranids can do it in a fraction of the timescale that it takes the Imperium. So whilst the Imperium can do it, its a huge resource investment to set it all up and keep it going long enough to get there. Plus they've so many worlds its easier for them to simply move resources around from shallower mines than it is to strip mine whole worlds. Same thing we do in the real world with resources; coals and minerals that end up too deep for economic extraction are left for more easily extracted deposits. You only go for the really tricky to reach stuff when the resource becomes a rarity or if very new technology comes along.


As for harvesting dead worlds; most worlds with Hive Cities are basically there already. Necromunda is like that; vast wastelands of blasted terrain with several vast cities rising up. Built upon mineral extraction and manufacture/processing

Isn't that essentially Apocalypse as well?

Being able to mine the entirety of a planet is pretty much a given for any civilization on the scale of the Imperium. Once you have cheap methods of getting into orbit you can basically strip mine entire planets. And with space travel you can probably get most of your mineral needs from asteroids or dead planets.

Mining a planet to nothing is still something that will take thousands of years, but it'll happen. I'm sure there are many worlds throughout space that have been strip mined till there is nothing but worthless rock even before the Imperium existed. DAoT stuff. Dead worlds covered in dust and gravel with long forsaken machinery dotted across their surface.

Also worth remembering the Cawl novel explicitly confirms that the Hive Fleets don’t strip everything. It’s more they go for whatever is immediately accessible, as one might expect from what is essentially a super predator of quite staggering scale.

Yes all plant and animal life will be scoffed, the air sucked out and surface water drunk - but there’s still stuff it’s just not energy efficient for the Hive Fleets to get into. And it’s those (admittedly scant) leftovers that Cawl’s regeneration makes use of.

Strip mining a planet is likewise an endeavour of effort and reward. Of course we can only guess at where The Imperium might draw that line, because their resources are simply inconceivable to us mere plebs. And nobody ever said they were that invested in efficiency.

Availability of resources is another consideration. Whilst there is an old, old fanfic eventually published in WD about the inefficiency of lobbing asteroids as a means of Exterminatus, it’s still something they’re capable of doing. Need water on a planet? You could take it from a comet or ice based asteroid, and Chuck it at the planet.

Will it work? I honestly have no idea. Ask someone suitably qualified. But would that necessarily stop the Imperium giving it a try, even if it’s just one particularly loopy Tech Priest, even if it’s just to see what happens? Probably not, no!

Interesting thing about Tyranid lore is that it starts out (at least by 3rd ed) that they are described as stripping everything.

Since then the lore that has them only stripping the most quickly accessible resources from a world. Plus also ignoring suns and gas giants and other big resources.


My impression is that Tyranids are feeding faster and with a focus on just making worlds basically inhospitable and thus mostly useless to other races so that other races can't quickly re-colonise worlds once they are fed from.
I've also held the view that Tyranids don't want to eat everything right now. They want to eat what they need to win the war and pacify the Galaxy. Then they'd come back around and feed more slowly or at least more fully and devour everything when there's nothing to threaten them and thus no need to expend resources making more warriors.

That’s certainly a possibility.

It could also be a recognition the Prey That Fights now knows the best time to inflict heavy losses is whilst the Hive Fleet feeds.

Yes the Shadow In The Warp makes that far easier said than done, as it also effects Warp Travel. But when Orks, Necrons and to a certain extent Eldar either don’t care or have ways round it, a Dine and Dash makes more sense, as to hang around after expending resources attacking the world risks losing even more to retribution attacks.

I’m sure there’s something in the background (and I’m not confident it was Kryptman), where The Imperium did just that with reasonable results. Cede the world, then detonate it whilst the Hive Fleet feeds.

Potentially, done enough times, that could be how you attrition yourself way to victory against the Hive Fleets.

Hell, the Necrons could, with suitably careful planning and the right will of course, use the Celestial Orrery to send a sun nova once a given system is infested.

The Imperium tried that. They used Exterminatus to starve a Hive Fleet by stripping worlds in advance of the fleet. In the end they still have to re-direct it into an Ork infestation and by the end the Imperium had lost many worlds and a huge amount of good faith from the population (you can push them only so far).


The other issue is that as a tactic, you are basically surrendering large swathes of territory for each Hive Fleet to burn itself out before you strike. This means your front line is constantly in a state of active retreat. Even the Imperium would eventually run out of worlds that they can sacrifice (keeping in mind the fleet is like a tendril so it doesn't hit the entire Imperium, but pushes into it).
Plus the Tyranids are a totally unknown quantity. You don't know if there's another tendril out there or another thousand.



Necrons could use this tactic, they have less apparent reliance on resources from worlds than most other races and don't need to worry about atmosphere or most surface biomatter. However they still want to be able to rule something, blowing up worlds would work longer for them (at least provided its not Tomb worlds) than most other factions, but it would still hit a point at which there's very little left.



Even with the vast size of the Imperium, its a short term tactic that comes with a lot of political fallout and the potential to be more self defeating.

Tyranids take everything of "biological matter". This includes rare minerals and stuff. But it's clearly shown in numerous sources that they leave the planets as basically dead rocks, little more than asteroids. So they don't take EVERYTHING. Perhaps this is a gap/oversight in the established lore? Because surely even in the bedrock comprised of the planet's crust there are valuable minerals and materials?

While I'm sure the minerals in a planets crust might be useful to the nids, they would be far less valuable than the biomatter. The Hive Fleet can always eat asteroids if they need minerals, but staying on a now dead planet for a few million tons of minerals seems like the point of diminishing returns. Such minerals can also be recycled within the hive fleet itself so topping off will need to be done less often.