Delete me please

[Jansviper]

Nevermind, figured it out.

[Eldariel]

According to CR guidelines, environment adds 1 to CR in this case and you need CR11-12 to make for a challenging encounter (~50% of their daily abilities, maybe character death) for a Level 9 party. CR is increased by two when doubling. So CR 5 is 2, CR 7 is 4, CR 9 is 8, CR 11 is 16 and increased to CR 12 by circumstances. So you need 16 of them, mathematically. That said, much depends on the optimization level of the party - a control Wizard could likely shut most of them out with one spell and a Chain Tripper Fighter doesn't really care about their numbers. A Druid would just munch them and overall, if your PCs are only hit on 20s, standard forms of attacks are pretty trivial.

Environmental damage, the trap, non-standard forms of attack and Aid Anothers or whatevers could make it more interesting though. Still, they better be worth their CR and preferably have some non-standard means to attack either saves, or touch, or unblockable damage (or some nasty effects if they hit) to truly count. Just taking 2d8+9 once per round isn't exactly the most hazardous thing ever.

[Jansviper]

XD Coincidentally, we came out with about the same math.

Thanks a ton Eldariel. >=3 Don't suppose you'd like to DM a Gauntlet eh?

[Douglas]

That depends on what you mean by "challenging", just how much the environment favors them, and exactly how dangerous the trap is. Going by RAW guidelines, "challenging" means CR = party level even though this should only take about 20% of the party's daily resources to beat and has low risk of actually killing a party member, so you (according to what the DMG labels with that word) want a CR 9 equivalent encounter.

Let's say just for demonstration that the environment is worth +1 CR and that the trap is CR 4 (yes, traps (http://www.d20srd.org/indexes/traps.htm) have challenge ratings just like monsters). Doubling the number of monsters increases the total Encounter Level by 2, so one monster (CR 3+1 for environment) plus the trap is EL 6. Add two more and it's EL 8. Adding a monster or group 2 levels lower increase EL by 1, so add another pair of monsters (EL 6) to boost total EL to 9. That's 5 monsters plus the trap and environmental advantage.

Whether this is actually challenging to your players or not depends very much on how optimized their characters are, and I wouldn't be at all surprised if your definition of "challenging" is rather higher than the DMG's definition. You'd have to quadruple that group to 23 monsters and the trap before the official EL and CR guidelines say it should theoretically be an even fight (i.e. 50-50 chance of the party actually losing, and probably dying), but the guidelines don't work all that well for groups that large and it doesn't take all that much optimization to be much tougher than the CR guidelines expect PCs to be.

[Eldariel]

XD Coincidentally, we came out with about the same math.

Thanks a ton Eldariel. >=3 Don't suppose you'd like to DM a Gauntlet eh?

I'm way too busy to DM anything right now, unfortunately (I was going to DM one of those class battles over here, but then half the participants got banned -.-). I'm only DMing one IRL campaign and even that's on hold as I get things sorted out for Christmas.

[Keld Denar]

The EL system is ok, but kind of abuseable if you want. I really like what Living Greyhawk used to do for the maths. First you figure out APL (Average Party Level). This is calculated by adding the ECL of all characters in the party, then divide by the number of characters in the party. If the party has 6, add one to this. LG doesn't allow for tables larger than 6, but I'd imagine you add 2 for 7, 3 for 8, etc. Then you round up or down to the nearest even interger, ie 2 4 6 8 10 etc.

Typical encounters in LG are EL = APL +2 to +3, with some special enounters being EL = APL +4. MOST modules don't have more than 2 fights in a day at this difficulty, although some do have a reputation as meatgrinders.

There are a lot of places where EL breaks down though. A common trick I saw some authors use involved non-associated class levels, and tacking on NPC classes to characters. A level 11 Wizard is CR11, but so is a Wizard11/Warrior1, but the difference is, the 2nd one gets about 7-8 extra HP, +2 fort save, and an extra feat.

Probably the worst thing I saw was a poorly scaling encounter that had Gauth beholders. They are only like, CR3, so 2 would be EL5, 4 would be EL7, 8 would be EL9, etc. 8 Gauth Beholders with Scorching Ray eyes against a party who's average level is 5-7 (APL+3). If all 8 Gauths fired Scorching Ray eyes at one PC, assuming 1 misses, that would be 7 * 4d6 or ~98 damage. I don't care who you are, NO PC can survive that much fire to the face, not at level 6 with typical WBL when you aren't expecting it. I never played in that one, but I heard enough people talking about it to know how dangerous it was. Laser beam deaths to all.

[Eldariel]

Probably the worst thing I saw was a poorly scaling encounter that had Gauth beholders. They are only like, CR3, so 2 would be EL5, 4 would be EL7, 8 would be EL9, etc. 8 Gauth Beholders with Scorching Ray eyes against a party who's average level is 5-7 (APL+3). If all 8 Gauths fired Scorching Ray eyes at one PC, assuming 1 misses, that would be 7 * 4d6 or ~98 damage. I don't care who you are, NO PC can survive that much fire to the face, not at level 6 with typical WBL when you aren't expecting it. I never played in that one, but I heard enough people talking about it to know how dangerous it was. Laser beam deaths to all.

That expects all the Gauths to have a LoE to the same targets though, which with proper scouting, is very easy to stop. Also, if you know in advance you'll be fighting Gauths (Divinations or scout), you'll of course have Fire Resistance up. Also, Gauth is CR 6. Not that it changes much. Having everyone with Uncanny Dodge approach in Total Defense (spending their standard action in total defense and moving each round before the encounter) helps a lot too. Basically, as long as you know they're there, you're ok. Of course, they have Dispel Magic, Sleep, Inflict Moderate Wounds, Paralysis and Exhaustion, but since the DCs are low (14), it's very rare for all of the party to be disabled (level 7 could have you meeting 4 Gauths, for example).

The real problems come when you truly abuse unassociated class levels. Pick up some lowish CR, preferably high HD monster, toss it insert unassociated caster class here and have your ECL 10 party face an epic caster with half a dozen epic feats, including Epic Spellcasting, and some 6-8 epic spells cast daily. Without trying, that's a one-turn KO. Dragons are really handy for this, for example; just pick non-Sorcerer casting such as Cleric or Wizard and go to town. As a bonus, they gain an insane amount of HD. Then use their HD-based Spell-Likes :smalleek: Of course, there's also the Ikea Tarrasque and the like, which is basically invulnerable to everything except Disintegrate (which you don't have at that level and which deals 1d6 points of damage per casting).