It says in the book that all creatures with the Tyranid trait are immune to heat, among many things, but how far does this go? For example I have an idea of a xenos race that among other weapons uses super-heated water, or some kind of gas, brought to an extreme level of heat and so used steam boil their enemies in a few seconds. But would the immunity mean that a gas cload heated to some 400-500 C or more would have no effect on the Tyranid? Because I kind of imagine that this would cause some serious harm to various organs and tissues etc.

Is it that I have misunderstood the "immunity to heat" part or are the Tyrands really to be uneffected by all kinds of heat effects/attacks?

They are immune to the heat, not to the flamers. We don't know exactly how hot promethium burns, but napalm's "work temperature" starts from 900 C. Even at lesser temperatures, superheated gases or liquids used as weapon will have additional damage factor - pressure, so I think your "steam-cannon" can affect Tyranyds even at 400-500 C.

In lore iirc, Nids are capable of landing on airless worlds, fighting on irradiated fields and even surviving in the atmosphere's of gas giants. So... unless that super-heated water gun is at a temperature approaching Napalm it'll probably just piss a Nid off. Remember that Nids don't have organs in the classical sense, or even tissues for that matter. Their bodies are more akin to robots built using biological means, as such they are hardened against environmental extremes in a way that naturally evolved creatures could never hope to achieve.

Thanks guys, I'll store my idea for a weaponized steam boiler for a while and give some other kind of weapon to deploy against the Tyranids. Boiled intergalactic shellfish/Tyranid did have a nice ring to it though.

How about overheated metal melt? Something like copper at 1400-1700 C under pressure. I have some micro-burns from such things, they carbonize flesh in a fraction of the second.

How about overheated metal melt? Something like copper at 1400-1700 C under pressure. I have some micro-burns from such things, they carbonize flesh in a fraction of the second.

I like the sound of that. I can definietly write up a minor Xenos race based around the use of molten metal in a weaponized form. Thanks.

Maybe something along the lines of the Reaper weapons from Mass Effect, not a good series if you're looking for realism I know, but perhaps a good source of inspiration. Then there are all the badass weapons from the Warhammer Fantasy Dwarfs, even Nids would balk at a line of Irondrakes.

don't give up on your idea of a steam based weapon just yet, even one that hurts nids. Have you ever read 'Martian odyssey'? It was a very early sf story that is still regarded as a masterpiece of the genre. It featured an alien with a weapon that fired glass darts.propelled by steamnproduced by mixing concentrated acid and water. Here's a quote if you don't want to get and read Martian Odyssey off the net where it's freely available. (You should)

Tweel and I were both armed. And by the way, that crystal weapon of Tweel's was an interesting device; I took a look at it after the dream-beast episode. It fired a little glass splinter, poisoned, I suppose, and I guess it held at least a hundred of 'em to a load. The propellent was steam--just plain steam!"

"Shteam!" echoed Putz. "From vot come, shteam?"

"From water, of course! You could see the water through the transparent handle and about a gill of another liquid, thick and yellowish. When Tweel squeezed the handle--there was no trigger--a drop of water and a drop of the yellow stuff squirted into the firing chamber, and the water vaporized--pop!--like that. It's not so difficult; I think we could develop the same principle. Concentrated sulphuric acid will heat water almost to boiling, and so will quicklime, and there's potassium and sodium--

"Of course, his weapon hadn't the range of mine, but it wasn't so bad in this thin air, and it _did_ hold as many shots as a cowboy's gun in a Western movie. It was effective, too, at least against Martian life; I tried it out, aiming at one of the crazy plants, and darned if the plant didn't wither up and fall apart! That's why I think the glass splinters were poisoned.

You could imagine your steam weapon mixing water and a potent acid mix in a chamber that instantly flash boils the water and expells it as a mix of hot steam and some acid. Does this help you?

Some creatures on earth can live at temperatures of up to 750 f, but these creatures do it at extreme depth underwater. Under greater pressure water doesn't boil as easily.

https://www.apexmagnets.com/news-how-tos/the-creature-with-magnetic-armor-scaly-foot-snail/

As to nid carapace armor...

http://inhabitat.com/three-layered-snail-shell-inspires-better-body-armor/

Some creatures on earth can live at temperatures of up to 750 f, but these creatures do it at extreme depth underwater. Under greater pressure water doesn't boil as easily.

750F is a temperature that such environement can have, but after 150C (302F) the cohesion of DNA starts to break down. Earth's hypertermophiles can withstand maximum 122C.

Some creatures on earth can live at temperatures of up to 750 f, but these creatures do it at extreme depth underwater. Under greater pressure water doesn't boil as easily.

750F is a temperature that such environement can have, but after 150C (302F) the cohesion of DNA starts to break down. Earth's hypertermophiles can withstand maximum 122C.

We'll I wish whoever wrote that article hadn't implied they were living at those temps then.

There is in the end no possible comparison to be drawn between Earth creatures and Tyranid bio-constructs. This is a race that laughs at the conventional laws of nature when it comes to what they can or can't survive, to the point where the lore depicts them as nigh-impervious to any natural or even man-made event up to and including Exterminatus.

And yet they can still be killed by massed kasgun fire...

And yet they can still be killed by massed kasgun fire...

Nobody ever dies to lasgun fire. They just shoot beams into enemy faces causing them to fumble and kill themselves with their own gun/grenade/walking blindly into ally fire. Bolters and Flamers are where the real fun is, cleanse with holy fire!

Thanks guys, some very good ideas. I most certainly like the water+acid=DEATH!!! idea, and I'll see if I can't find time to look at the "Martian Odyssey". If anyone has more, please keep it coming.

Martian Odyssey, tho of course horribky dated is still regarded as a classic sf sorry that helped mold the genre'.