I'm not surprised it was nearly a TPK....
5 CR 6 creatures is pushing CR30 for the group....

d20srd.org's encounter calculator only places the encounter at very difficult. While that's hardly the last work, several CR 6 creatures shouldn't be a TPK for a level 8-9 party.

To the OP, the CR is reached by playtesting. CR 6 means a party of 4 6th level characters used 20-25% of their resources to defeat one of these creatures. There isn't a real breakdown of how a CR is decided beyond that, excepting that PC Class HD = CR

I usually figure that two sixes would make a seven or eight, so two sevens would make a nine or so... challenging but doable.

I do however flub that when I have constitution damage monsters. That can get nasty fast...Imagine taking 18 damage, then losing 6 points of con means you loose another 27 (6 means -3, 3 times 9(level)=27) +18 = 45 "damage" from one attack.

If you're not sure, attack the party with half, then have the other half join in "if things go poorly for the monsters"

bad party tactics?

Not really. They were expecting something tougher later, so they weren't expending their serious top-notch powers at first. That changed after the Bonedrinkers walked through two fireballs and laughed at the cleric's pitiful attempts to turn them.

Now, if they knew they were going up against grappling critters with DR (bypassable by silver or good), they could have prepared for them. This wasn't such a case.

1) You're throwing an EL 10 encounter against a party with an average party level (APL) of 8.5 -- which I round down to 8, so there's one possible problem. Assuming a four person group, what I call the Party Encounter Level (PEL) would be either 8 or 9

2) Just because a creature has Improved Grapple doesn't mean they use it automatically. Judicious use of this ability can help mitigate some of the threat without taking the thrill of the fight from your players.

3) What state was the party in going into the encounter? Fresh? Badly beat up? That makes a big difference in an encounter.

4) What was the party's response to the encounter? Poor strategy, mistakes, even bad die rolls can turn a good situation against you.

5) Did you roll the critters' HP or did you go by the average (93 hp)?

Based on what you say, it sounds like you threw too many at the party. Moving forward, if there's a creature you want to use that you're not certain about, give the party a "feeler" encounter with an EL 1 or 2 lower that the APL. CRs sometime assume the players have some knowledge of what they're facing, so take that into account as well.

Really, from the Bonedrinkers' point of view, grappling is a superior tactic.

Six members of the party (gnome rogue, gnome sorcerer / rogue, elf wizard, elf fighter / swash / dervish, halfling cleric, human ranger), well-rested, beginning the encounter in badlands scrub (the Thornwaste from "Red Hand of Doom," if you're familiar with that) at 80' or so.

I went with average hp.

It may not be a superior tactic against a group; when grappling with an opponent, you're fully occupied. If I recall correctly there a 25% chance someone outside the grapple accidently targets an ally rather than the enemy, but that's a risk worth taking. If they're intelligent undead, then they'll know when not to grapple. Also, they may decide to subdue a PC when they're reeling and on their last legs so they can feed while they're fresh. With a five versus six group, it's not to their advantage to try to grapple and feed unless they can take the party completely by surprise. With a Ranger in the group that's damn near impossible.

So, assuming that halp the party is 8th level and the rest are 9th, then the APL as I said before is still 8, but the PEL is more like 9 (how I do it: figure out the EL for the party and subtract 4) which means it's still gonna be difficult.

Well the party's effectiveness is curtailed slightly by a few things, based on what I see here:

1) The rogues are slightly nerfed by the fact that sneak attack doesn't work against undead, which means they might be less likely to go for the flank. Same thing if the ranger has undead as an enemy -- he can't apply the damage bonus because they can't feel pain.

2) One Cleric for 6 PCs makes a rough ratio sometimes, turning notwithstanding. I'm assuming the Cleric made an attempt to turn at the least.

3) Not having my materials before me, it seems that you're lacking in a PC that can dish good melee damage. Sometimes you just have to hit things harder to overcome DR.

These are by no means faults with the party, but things to consider when designing future encounters. I noticed later in this thread that you miscalculated the EL, and that's probably the biggest reason why things went wrong. I'm pretty much with the consensus: five was too many.

The CR system isn't perfect by any means. At all. Practically ever.
The idea is to give you a quick guideline as to what to expect, not to follow religiously.

Next time, playtest the monsters. You probably have a quick copy of your players' character sheets / combat stats, right? If not, get one. Then before the adventure, if you plan on using these creatures, do a quick playtest. In the playtest, did the party trounce them without using any resources? That probably means that the party will use around 10% of their resources. Did they use around 10%? That means in reality, it'll be 25%. The party will always be more challenged than you think.
If, in the playtest, it was a narrow victory only achieved by particular strategies, you're in trouble.

This is about the only advice I give for such things. Personally, I only use the Monster Manuals for pretty pictures and make up my own monsters on the spot - ones I know the party will be appropriately challenged for.

If you don't have time to playtest them, when using a new/unknown creature then be ready to tweak on the fly. Secretly scaling HP is an easy one. Have one or two of them make tactical mistakes. Not complete "impale your brother monster" stuff, but little stuff. Remember that monsters usually know little about the party. If a PC has special resistance, "accidentally" use an ineffective ability against that person. Have them use mental effects on mages or Fort save abilities against tanks.

If the environment allows it, you can always start with a reduced number of baddies and have friends show up.

Yeah, this would be a rather tough encounter. My question is, how large was the party, and what tactics did they employ against the beasts? Once these monsters get in close most mid-level characters are in trouble. . . . Also, I am curious what tactics the party used, and what the breakdown was in capabilities. I think this is a pretty challenging encounter, but not a slaughterfest in the making. It's close enough that the circumstances would make a big difference.

Five CR6's would be rough for an 8th level group. Rougher still if they didn't have a cleric or any special undead precautions or they were low on resources to begin with. Two or three might have been a bit better.

How close to a TPK did you get? (ie, how many party members dead?)

If you didn't actually slay any party members, then you actually did ok. That would have been a tough encounter regardless.

How close to a TPK did you get? (ie, how many party members dead?)

None. Two with Con damage, others with negative hit points.

Chalk that one up to a close call then, you did ok. :)

You're looking at +2 to EL (or CR, the two should be interchangeable even if they technically aren't) every time the number of critters doubles. Two bonedrinkers is 8, four is 10, and five would be just a bit tougher. While it shouldn't have been a TPK, it was still really hard on them--not helped by their not using better skills and powers. Honestly, I'd say it's a scaling problem, and you should keep the "double monsters, +2 CR" rule handy in the future.

I've done this once or twice, too, and it's really just getting used to it. Once you figure out the numbers properly, it's equally important to look at any abilities the monster has and decide how that meshes with your PCs' abilities, if only because some monsters have abilities or weaknesses that can make things hugely difficult without someone with the proper abilities in the party. Undead with lots of HD are a big one, especially if your cleric doesn't have improved turning or something else to boost his attempts, as are creatures with spell resistance that belies their CR, which can be particularly troublesome for casters who might be multiclassed or concentrating their feat selection elsewhere. Once you get your math right on getting a proper EL, you need to look at exactly what your PCs are capable of and what kind of things they can handle.

You're looking at +2 to EL (or CR, the two should be interchangeable even if they technically aren't) every time the number of critters doubles.

Ah, there's my trouble, I think. I've been running "EL increase of one every time the number of opponents doubles."

Your future tactic is very sound.

>_> Personally, I would have cut my losses, left the weak to be eaten and ran for the hills. There are always new friends to be made.

The cleric has enough experience to be 7th level, actually. Just because the player chooses not to advance a level "in the field", doesn't mean he couldn't.

Would that have made a difference in the fight? I think so.

A) If you use grappling then it only takes X number of one size larger creatures to kill a party of X sized medium sized creatures. Larger creatures are infinitely superior in grappling. Overrall they have higher strengths and get a built in +4 to their grapple check. So. If each creature grapples a PC, the fight's over. No big surprise there.

B) 5 CR 6's is at least an EL 10 with a 6 left over. So, that's an EL 10-11 depending on circumstances. Push it even higher if the area is favorable to the creatures and not to the characters. It's not surprising that an EL of +2 to +3 to come close to a TPK - especially when the encounter is composed of creatures near to the characters' level *and* when there's as many if not more of them. With that many creatures, they can just overwhelm the Fighter, Cleric, Wizard, and Rogue design of the game.

I got 10.6 too.

Undead CRs are calculated on the basis that there is a Cleric in the party who will try and turn them i.e. that it will be cakewalk some of the time and harder than a usual CR6 the rest of the time.

(Though a ninth level cleric could only take one, or rarely two, each round if they rolled 16+)

Anything like Shadows that does a funny sort of damage is brutal in multiples too.

According to the Encounter Calculator, 5 CR6 creatures is an EL 11 encounter. So if your party was level 8, that should have been a pretty damn difficult fight. If it was closer to 6 or 7 as your player suggests, then no wonder they nearly died. Even if they're closer to a party level 9, then it still could have been close because of bad rolls or just because of how they match with your particular party.

But yeah, CR system is not very reliable. Guidelines only, my friend. Guidelines.

If you think the Bonedrinkers are bad, check out the Drowned... Cr 8 I believe, yet I took out a party of 4 12th level characters (no cleric- idiots)... Something like 20hd and if you get within a certain distance, you drown... Nasty nasty nasty... They work well on boats... *insert evil chuckle*