During our last game session, my player went on Rain hopping to restock their ship with fresh food (only to discover that everything on this world was inedible). Furthermore they noted that their records were inexact: there were no more inhabitants on the planet. So, my player made a short investigation in the abandoned colonies only to find notes about strange ruins discovered in the jungle and the curious noise of the rain around them. Finally they went off to achieve their current endeavour, but they plan to come back to Rain sooner or later to investigate what happened there expecting to exhume some xeno artefact from the ruins.

The only information I have gathered about Rain are those found in the Rogue Trader Core Rulebook, and I’m lacking imagination to build an endeavour on this planet. Has anyone ever done a Rain based endeavour or fleshed the planet out themselves? Any extra info or stories would be welcome.

I wrote up my own backstory for Rain based off of the information provided in the book.

The basic summary of it is that there were Xenos races in Rain, but they are long dead now. Thousands of years ago in their hubris they began engineering plants that could support their ever-growing population and be ever-so-slightly psychically active so that they could taste like whatever the being consuming them wanted. Tragically, mixing Warp energy with plant life was not a good idea, and the plant life slowly grew to cover the surface of the world. The plants themselves are generally indifferent towards life on their surface, but once people start taking cuttings or clearcutting areas for their bases, they begin to react.

Once you've breathed the air on Rain you've been infected with the spores from the planet. Since humanity (and other races) were not the intended recipients of the plant life, the effects are not instantaneous. However they are still in your body and soul, gradually figuring you out and working towards driving you mad. During the vast rainstorms of the planet, when the water drowns out all other sound your brain slowly starts to subconsciously react to the influence conjuring up sounds and images in an attempt to warn you that something is wrong. Once a critical point has been reached though, your mind violently breaks and you start attacking everyone and everything around you, before finally killing yourself.

The ancient Xenos on this planet, realising the threat posed, began building their cities underground, deeper and deeper into the planet. They went as far as their technology could take them before attempting to re-establish their civilization and find a way to reclaim the surface .Unfortunately they still needed air to breathe, and even in faint amounts the plants would attempt to take control of them. Eventually the roots of the plants even reached their great underground cities, and they themselves succumbed. The cities are still there, covered in the roots and vines of the plant life above, and teeming with ancient bio-engineering Xenotech that the more radical members of the Magos Biologis would pay handsomely for.

Unfortunately without psychically warded vac-sealed suits setting foot on Rain is an eventual death sentence if you remain there. Mechanically I have it that once the planet regards them as a threat, everyone on Rain must make Willpower Tests every d10 days, with a modifier that starts at +60 and then decreases by 10 every Test failed or otherwise. NPCs that fail this appear to act normal, but when the next rainstorm comes a combination of paranoia and control cause them to snap and fly into a rage attempting to kill everyone around them. Treat them as Frenzied, immune to Fatigue and any Critical Hit that does not cause death does not slow them down.

PCs that fail still make Willpower Tests, but gain d10 Insanity with an extra d10 for every 2 degrees of failure on the test as their mind starts to rebel against them. Until they become aware of the dangers of Rain roll this insanity secretly, and just inform your players of how they're starting to see things at the corner of their vision and feel that they're being watched. Only if they recognise the danger and escape Rain let them know exactly how crazy that planet drove them. This insanity will slowly fade (similar to Characteristic damage) once they're off world, but for every test they failed down there they gain 1 permanent point of insanity.

If they manage to reach the underground cities there are psychic blockers and research that can help innoculate them against the disease, but the Flora down there recognises the threat and will engage the party in combat. Roll up some Monstrous Flora from Koronus Bestiary to serve as guardians. Ultimately killing these plants do nothing, as more will grow in time and there is no "central node" that can be destroyed to wrap this up nicely. The Xenos research has a way to kill all of the plants, but by doing so you would also destroy the soil and Rain would be lost as any sort of potential bonus to the Explorers.

Have fun!

Thanks for your reply Erathia.

I like your idea of a race whose intentions were good but resulted in a disaster. The xeno race possessed certainly a wide knowledge about genetics, but they were too ambitious! A good warning for my players who are exploiting the conflict between Chorda and Winterscale.

Rain's "official" backstory continues in the Deathwatch RPG where it is mentioned that a Deathwatch Kill Team investigated the world and was set upon by hordes of Dark Eldar.

I like your background. I used it as part of my huge Yu'Vath Reborn campaign.