So you have a campaign in quite a different genre to survival horror. Perhaps you are running a High Fantasy Dungeons & Dragons game but you want to delve into something a little darker for a session or two. Or perhaps that Political Thriller Vampire game has sent that unlikely coterie of vampires over the threshold into a Hisil Wound. Heck, perhaps you're running a relatively similar genre like a Call-of-Cthulhu style investigative horror game.
In any of these instances, you've drummed certain trope-like bahaviors into your player's minds (and their character's actions). The High Fantasy players expect to face every physical confrontation and win with few, if any, casualties. Monsters are to be beaten. Shiny objects are to be stolen. Cursed items are few and far between. Obviously, if you're running monsters several CR above them that they're meant to run and hide from -- they're screwed. The Political Thriller Vampire players expect to backstab each other, jockey for position, and pay attention to every which what word is spoken by the others - and thus can often self-destruct their entire party within an hour of a Survival Horror.
Rather than begin a process of re-training (which is often painful enough in the first instance unless you provide your players' with a list of genre expectations), there are a few environmental signals and cues that can often trigger a new set of behaviors. Firstly, let the players know to prepare for an adventure that is a little different and that you're playing with another genre (you don't have to say which). That way all of those conscious positive 'meta-game' considerations like 'attack the dragon even when a sensible person would run like a little girl' don't crop up.
It also gets the players curious and heightens their interest, while letting them know that you haven't just gone mad, there is a purpose behind the re-design.
Then find a way to transition between the two genres. The High Fantasy adventurers are riding across green hills, dealing with bandits and the usual issues, but then the grass is more yellowed, there's darker clouds perpetually over the horizon (that they'll soon ride under) and the bandits they confront are covered with oozing sores and rather than attack, they plead for their lives and an escort to prison.
The Political Thriller Vampires soon realize that a prominent Carthian and Invictus elder who are normally at each other's throats are actually working together on this one ... and they're being genuine about it! They're paranoid about each other but genuinely wish the group well and are too busy trying to ensure success of the operation that they don't plan how to ruin the other (at least not until after it happens). Why? Because that haunted house (with the Wound threshold) is considered to be too dangerous. Local vampires near the area have turned draugr and had to be put down. It's impacting on the Masquerade. Its influence is spreading.
Don't skimp on the transition period. Even if you're tempted to just Teleport your adventurers into the Survival Horror or have a higher up simply order the coterie into the property, don't do it.
Not only does a transition period assist with pacing, building anticipation and dread, and activating both the player's curiosity and imagination, but it provides one other very important function. It allows the campaign to make sense even as it warps into something new. The new tropes don't clash with the old, they contrast with them, play with them, and build something new and more interesting. In the end, the survival horror plotline should be so woven into the campaign that rather than feeling like some aberrant growth caused by a DM's or ST's fancy, it's actually a vital part of an ongoing campaign.
During the adventure, keep providing plenty of clues as to when they should discard certain tropes.
Show what happened to the last coterie that investigated the house and how their pettiness tore each other apart (notes detailing greed stashing away vital objects, diary entries on how revenge will be sort for a prior indiscretion, forensic details, a babbling draugr still caught in a past conversation). Sure, the new coterie will doubtless still bicker and fight but it'll hopefully be in the manner of your usual group-based survival horror. Strain and tensions mounting that seek release in bitching and arguments. Not conscious efforts to destroy other team-mates simply to bring about their end.
I'll do up a big post on Horror in High Fantasy tomorrow as it seems to be growing a little too large to insert here.
Then, you have one final detail once they have survived the enemy, possibly to escape, possibly to end the infection or strike a final blow (a slight differentiation from the usual survival horror where the goal is to survive to reach the center rather than to survive to escape). You have to cap the adventure and transition back to the regular genre. Your best bet is to show that by saving the day, the character's have successfully re-established the old expectations.
The clouds drift away from the castle and all of the signs of spiritual decay wink out. Now let the High Fantasy party of heroes mow down all of the significantly weakened antagonists they have yet to kill. Heck, if you want a real book end, have them attacked by regular bandits out for their gold once they re-enter the free lands.
The Political Thriller Vampires return to report their success to the Carthian and Invictus elder and immediately the two start bickering and trying to blame the other for prior failures. Or there's a glint in the old enemies' eyes as they regard each other anew for the coming days. The vampires soon find out that the status quo has been well and truly re-established.
Then continue on with your campaign, now masterfully pulled together, until the next time you'd like to digress from the 'usual programming'.
Oh, also, you can find a list of the other articles in this series here.