Need Seasoned GM's Advice on Fight Difficulty

[Minandreas]

Thank you in advance for taking the time to read this and give me your advice!

I have done some GMing of games for the past year or so, but they have always been games of 5 or so players. I am hosting a Halloween one night only game, and it got more popular than I anticipated. 11 PC's to be precise...

The books say that when determining difficulty, if there are more than 6 players, simply add 1 to the APL. But going from 6 to 11 players is a pretty massive difference, and I don't think simply adding 1 to the APL is going to be enough to make the fights challenging... On top of this, since it is a one night only session of 3 battles, everyone is power gaming HARD. People are ignoring the idea of Role Play entirely. They are all level 12, and have by the book amount of gold to spend (108,000).

So questions are...

What would you recommend I consider their APL (Average party Level) when determining what monsters to throw at them?

Do you have any particular advice for how to design such large scale fights?

Thanks again all!

[Brambleman]

Use many foes, and give your monsters some kind of terrain advantage.

[Lathiira]

I'd consider the APL as follows:

Character level: 12
Power-gaming: +1, maybe +2
Party-size of 11: +2

So for safety's sake, they'd be APL 15. You literally have enough PCs for two, nearly three full adventuring parties and they're powergamers. Throw lots of foes at them, let your bad guys buff in advance, hostile terrain at the least should help (and I mean hostile, like fighting on a lava field beside an actively erupting volcano or worse). Pull out all the stops.

[EWHM]

With 11 pcs, you've got effectively 2-3 balanced parties in play. What's more, they've probably got most of the force-multiplier classes in effect also.
So my recommendation is 3x to 4x the numbers of foes. Don't raise the CRs much, just add lots more bodies. Oh, and get yourself an assistant GM, and I highly recommend also getting some mostly-retired players to show up periodically as guest stars controlling a BBEG or major minions of same.

[Minandreas]

Sweet, thanks guys. I really wasn't sure what to do with the APL so the 15 helps a lot. Terrain will be a bit difficult to give too much advantage with due to the location it is happening at, but I can definitely have the enemies EXTREMELY well prepared for the battle. Full on buffs, plenty of traps, etc.

[LordHector]

EWHM wrote:

Oh, and get yourself an assistant GM

I can't reiterate this enough. With that many enemy bodies, it's going to be HELL to run them all. Not only will an assistant help with running half the baddies for you, but can also help keep you strait on rules and look up things for you while you keep the flow going. I could make the difference between a nightmare (the bad kind, not the 'Oooh, it's Halloween!' kind) and a very memorable gaming experience.

[Minandreas]

LordHector wrote:

EWHM wrote:

Oh, and get yourself an assistant GM

I can't reiterate this enough. With that many enemy bodies, it's going to be HELL to run them all. Not only will an assistant help with running half the baddies for you, but can also help keep you strait on rules and look up things for you while you keep the flow going. I could make the difference between a nightmare (the bad kind, not the 'Oooh, it's Halloween!' kind) and a very memorable gaming experience.

Ya, as soon as the number of players hit 8, I asked one of them, a good friend of mine to help me GM instead. So I'm set on the assistant. I appreciate the input though! Had I not prepared one already this would have easily been the most important bit of advice I could ever have received here X.X