My players are a Slaanesh Renegade sniper with a Legacy weapon a Tzeentch Idolitrex Magos of Forge Polix with Precog and pyro powers and a Pirate Prince who is to be blamed for this.
The group returned to their old base of operations to buy some new kit only find their dice had turned on them. The Renegade failed to buy some slaves, the Magos tried to buy a Multi-Melta then got 99 on the reroll so I told him he got it and the Pirate Prince (PP from now on) rolled for and got a Ghibeline Hyperwave Clarion Cannon (as he had Excessive wealth I said he paid cash).
The group set out to find out why the name of the Gray Talon no longer gained any respect when once they were hailed as hive city slaying heroes and went to see the lady who ruled this 16th of the demon world they were on only for the Renegade to fail his/her (Hermaphrodite) charm roll and get told his former lover would not see him until they made peace with their host and so they went to a temple of the Damon Prince who owned the planet.
Once there they got an audience with the guy in charge and got to work finding out how they had offended his master and pleaded their case. Some good role playing the gift of a Multi-Melta and a charm roll got the priest to agree to contact the Damon Prince and explain and as said priest left PP decided he was offended that the Damon Prince had not shown up first and tested his new gun on the priests back.
The Demon Prince became aware of this began to manifest and read minds (not being the sort to jump to conclusions) before TKing PP out into the street. PP made his Agility roll and his spine hound with his gun came to his aid. Then died.
PP sans gun decided to GTFO and ran and the other two, knowing they needed to be on their best behavior and seeing the place in chaos, started looting.
Stuff happened but as it's not that funny (when looting they learned of a book the Demon Prince took from some of the Emperors finest and the Magos did make a -20 Infamy roll to get another Multi-Melta and stuck a Flamer of Tzeench in it giving it warp weapon) and then they stole a bike so they could try to reach the rift in reality the Damon Prince called home and get that book.
Magos got 90 odd on his roll to keep safe as they traveled into the rift and I ruled that they ended up in orbit of it instead till PP flew in with his dropship (Demon Prince had taken his ship at this point) and and took them in.
I gave everyone 300 xp for saving me doing any work and called it a night so the group would have their rerolls for what comes next.
WHAT THE HELL DO I DO NOW?

My players are about to face a Demon Prince that is pissed at them knows the battle field and has backup.

I personally don't see why you should save them. As it is their own fault and a lack of luck they should very well face the consequences of it. Let them die. Let them burn some infamy and then maybe get them to work harder to repay their debt to the Prince. Or start a new characters.

But, if you're so determinded to let them live. Well, why don't they just summon or meet another daemon and get help from him, for example? Or maybe find out some sort of portal on the planet or near it and escape. There is still great many ways to kill them or let them live. It's really up to you as a GM. If they can't devise a proper escape plan or whatever, it is only fair that they die. (And again, yeah, they can burn infamy and maybe miraculously survive.)

That's plan B I partly want to work out my options if they need to burn infamy. The funny thing is the Demon Prince only objected to them going and getting a Dark Patronage with another demon and they could have talked their way out. I guess I should stat this guy up so he can kill them.

Does the Daemon Prince in question have any rivals? If you didn't write it up as having rivals, introduce some now. Possible the Master of Forge Polix or one of the pirate bands in the area have agents nearby who wish to capitalize on the chaos.

If that happens, there are three ways of handling it off the top of my head:

1) the agents in question contact the players and offer them assistance, either in combat or in concealing the group.

2) the agents in question contact the rival group and a Forge Polix or pirate fleet shows up to wreck some havoc in-system- the daemon prince now has bigger fish to fry, and the players have another group they can try to get in good with or suborn (I imagine that the Idolitrex Magos wishes to take over his forge of origin, and I also assume that the PP would like to expand his fleet)

3) the agents put into action plans on the ground and begin a planet-wide campaign of sabotage and incitement of riots. This gives the players fewer clues regarding who took what actions, but the daemon prince still has bigger fish to fry.

These cases are all more-or-less deus ex machina, but they all make sense *and* have the virtue of being built-in plot hooks. More than one group could be involved too, resulting in a three-or-more way Mexican (Catachan?) standoff.

The Demon Prince has a Lord of Change who wanted the book the players are after so that might come up but the group have just gone in with no plan and no back up. Demon Prince has already taken PPs ship to stop it attacking his world and the Magos has not too many friends due to his for the LOLs take on life so all that leves is whatever ground forces they got down.

Screwed doesn't begin to cover this does it?

Mayby they'll suprise me again and live thru it.

The whole point of the rival faction idea is to introduce accidental backup. It's not a card you can play more than a few times without the players saying 'this is contrived,' but you can easily get away with it once- and it can introduce broad-scale plot hooks.

The Lord of Change turning traitor might be interesting.

I'm thinking LoC attacks DP and the players are sidelined as they try to survive could be fun.

I'd still expect the DPs minions to be after them, so they wouldn't be complete spectators, but something like that, yeah.

I dunno, an LoC is frequently unpredictable and it could be seen that the death of the Prince is furthering their own convoluted scheme. In such a situation if your boss is being attacked by a personification of Tzeentch, I would imagine minions would forget the person that the DP would be mad at and work to defend their lord and master. Even moreso, an LoC could in theory manipulate the mind of the lessers to their own goals, twisting some of them around so that they fight their own boss.

Having them escape from a warzone as two mighty champions clash, could allow them a rather tough challenge, avoiding potent warp blasts and gunfire from both sides.

We're talking about a DP that controls a world, right? That means that we're talking about minions on a planetary scale. There may well be some sort of bureaucracy.

Imagine for a moment a crazy scenario: the European Union actually unifies and becomes a single nation. The United States decides that it doesn't want another superpower competing on the global scene and invades the Iberian peninsula and the coast of Normandy. Does the entire European war machine turn to fight it? No- they keep units in reserve and they keep sentries in place, just in case Russia decides to go all Soviet Union 2.0 all of a sudden.

So soldiers may well still be after the PCs. It takes time for new orders to filter anyway, unless the DP is capable of planet-wide telepathy, so many units probably won't respond to the LoC's betrayal until everything but the crying is over- which may be part of the LoC's plan. After all, if the PC's get away with the book because he provided cover, that would look pretty stupid, but if he's relying on the slow reactions of the bureaucracy to capture the players while he handles the DP, taking his position...

Well. I'll just leave it there; the LoC may have already mapped it out.

Two things I want to clear up. The Demon World looks like an 8 pointed star (the chaos undivided symbol) with a glowing rift in reality in the center in to which the players are heading so DPs backup needs him to let them in (it's ment to be his safe place) and the LoC never worked for DP (my bad in explaining it the way I did, when I said The Demon Prince has a Lord of Change who wanted the book I ment DP had a LoC after him) LoC was incharge of the raid that the book was taken on and DP is trying to work out how or why he got away with it (he knows somone is saying "Just as planed" and wants to know who).

A DPs power is generally a fragment close to that of a Greater Daemon. There are a few rare princes who can overpower one but these are few and far between. As Annaamarth mentioned, this could be all to his plots and unless the prince can get the entire planets support immediately (which is very unlikely) odds are the immediate group of people can be easily coerced especially looking at an LoC Psy Rating painful and silly WP (Yet to find a BC equivalent but PR 9, WP 18, Unnatural WPx2 etc going on Deathwatch Rules). One half powered mind control ability from any of the 40k RPG books can easily take command of a few weak willed minions.

It would likely be in his best interests to keep the party alive so that he retrieves the book. Worst case scenario though, random warp anomaly

Both DP and LoC know the odds are someone is pulling stings and both know it's not them. I have no plans to think up who it is and am assuming DP got lucky but the plot may change that.

In combat between the two LoC has the stats but DP has home turf and a few tricks that the nature of his rift and the book (an Eldar fate map the Gray Knights were using to learn demon true names) have let him hide from LoC.

Yes that means an unaligned Demon Prince must out plot a Grater Demon of Tzeench!

TPK seems appropriate here. When players are stupid, you can cut them some slack. When players are straight retarded, killing them all off teaches them valuable lessons.

There is that yes. I did say "you know in Dragon Age where you bang that gong to fight that dragon and it asks if you're sure about 3 times? this is me doing that."

They should already know. If you want to be extremely nice, you can give them another warning or 2. I wouldn't, but that's just me.

And, if I were in your shoes, I wouldn't even play out the combat. It would be a "rocks fall, everybody dies" sort of thing. Three random dudes fighting a daemon prince shouldn't have a chance in hell, so don't let them skate out by luck. Or, surround the prince with a large group of minions. This should be an epic bloodbath.

Lessons clearly need to be learned by these guys.

There is another option...Daemon Princes can show mercy if it benefits them. Whats the alignment of this prince? Khornate, Slaanesh etc.

If he's anything but Khorne and you can think of a reason why their continued existance might be of use to him, what about rather than the rocks fall ending or such, could you possibly figure out a way to have him dominate them. Brand them with his own chaotic mark which applies various unpleasantries. Forcing them into becoming new (if albeit unwilling) servants He might be the kind of prince who wants lesser subordinates or something? I dunno...throwing ideas out there! Then you can keep them alive and mean they have a new threat to consider, how to remove his dark image from their body/soul.

DPs unaligned and the highest infamy player is in the 60s so their not random dudes. I think I know how this will go down. 29 hours till I find out for sure.

Agreed. If they can't come up wit a good plan, Give them an epic minion-slaughtering bloodbath, drag them in front of the prince in spiked, skin-flensing chains, and have him explain that he is NOT happy.

If you want an 'out', let him give them a suitably suicidal and/or unpleasant task, and send them off, complete with suitable scars to remind them who they're now working for. I suggest 'curse-brands' (no need to be specific about rules but something that lets him track you down and know what you're doing) and half of one hand removed from each player character as an 'idiot tax'. Daemon princes tend not to be nice individuals...

I'm starting in about one hour. Just need to stat DP and let RIP!

I'll post how it goes for you all.

OK so DP goes by the name of Vevzar and had

WS BS S T Ag Int Per WP Fel Inf PR

65 60 50 60 60 60 60 70 75 130 6

Demonic 3, Wings etc.

Group landed (1 reroll used) and set out to find the book. A good roll to navigate got them overlooking a large(ish) room that looked like it was used for demon binding and Magos sensing DPs aproch went down, Renegade hides and PP drinks and does drugs (then rolls stupidly good on toughness and stays upright). DP shows up and attacks Magos (who dodges), Renegade shoots DP ( I used DoS vs DoS as DP had a dodge of 110 when all's said and done) and 9 damage - 6 TB - 3 Demonic = ping! Magos hit with his Multi-Melta for 20 damage and PP used the stun rules to show that cheep tricks work.

Next round Magos is oneshoted into crit by Hellish Blast, DP takes more Multi-Melta damage and then moves the wall to keep PP and Renegade out of the fight.

LoC shows up and Magos attacks it, as does DP.

DP had set up this room as a trap for LoC and used the book and the room to start binding him, says to Magos "Keep him here and you will live" and flys up, brings a sword down into LoC and starts binding him into it. The others to try to send a call to the demon they have the Dark Patronage with and offer the number of souls Dr Evil would want for an exit and pass a -10 infamy test (I would have said -20 but a number that high has it's own power). More rolls than I would call fun later (not too many it was just the same 3 things being rolled 7 turns in a row) and DP with the help of Magos have bound LoC in 3 swords that occupy the same place and just how ready DP was for this is seen (the sword went into the floor and more binding happened) and DP took Magos somewhere he couldn't make trouble, got the other two and explained that the demon they had Dark Patronage with was paying for their release and dropped them off by their ship so they could see that he had given it to the Word Bearers. PP (who wanted to start a new character as he hes lost his ship) started shooting and died.

DP took 50 damage, used 4 rerolls and I forgot to use his Fear rules.

Thank for all your help guys.

You did many mistakes to put yourself in that situation.

He put a daemon into a flamer he just acquisitioned? Yeah, or not. How do you acquision a flamer that's wrought for purpose or has legacy of slaughter without your say-so? You can't.

Unless their Infamy is really low, you literally can't kill them.

So what are you worried about?

EDIT: And what Brother Tearer said. Why did you let them do this stuff?

A lot GM's would rather let players break the game than upset them by saying no.

Word of advice from a 20-year GM: During character creation, say no more than you say yes.

You did many mistakes to put yourself in that situation.

He put a daemon into a flamer he just acquisitioned? Yeah, or not. How do you acquision a flamer that's wrought for purpose or has legacy of slaughter without your say-so? You can't.

Mostly by not double ckecking the rules as he made it I'm afraid. I'll blame LoC and screw him over later.

And it was a Multi-Melta with a Flamer of Tzeench in it.