How do you make an encounter actually match its CR level?

Question

I recently started using encounter generators and tables. I've noticed that there are encounters like "8 Cave Spiders" or similar. While the number of enemies will result in an encounter that "should" be challenging, each creature's turn is limited to a 1v1 encounter with a player. Because of this, the player's statistics tend to make combat futile for creatures under a certain level (can only hit and save on natural 20s, can only affect players with spells or dodge players attacks on their natural 1s).

Now, is there a way to take creatures that fall into that category of 5%ers (1 in 20 chance to do anything) and make them do something useful more than 5% of the time under RAW?

I'm not asking how to modify the encounters to produce creatures that aren't 5%ers. I'm asking how to take those encounters as written and make them as challenging as they're supposed to be.

Answer 1

The ways to make monsters more challenging is to use 'player' tactics such as flanking, ambush and aid another.

Using giant spiders as an example.

Round 1 Check for surprise vs stealth (with a +14 for the modifier 11 as the base and 3 for distance). Assuming spiders get surprised, nail the PCs with eight touch attacks with web (at +5 to hit).

Round 2 PCs must get out of entanglement or take the penalties (an entangled creature moves at half speed, cannot run or charge, and takes a –2 penalty on all attack rolls and a –4 penalty to dexterity. An entangled character who attempts to cast a spell must make a concentration check (DC 15 + spell level) or lose the spell). Meanwhile spiders go after the lightly armoured types to get flanking. A couple stay back to web anyone getting loose.

Round 3 If spiders are still having problems hitting (and it is not just bad dice) they start tag-teaming with aid another to up higher.

At this point or sooner, depending on how tough your PCs are, the spiders are hitting with a +8 and starting to poison the lower STR PCs while the martial types are still getting hit with entangling every round.

An interesting read for low CR, high threat concept is http://www.tuckerskobolds.com/.

Answer 2

I use a mini-mass combat system inspired by the mook wads of Feng Shui. It is mainly designed to simulate squad on squad combat that the PCs are involved in but it also works to amp up the threat of a host of little critters.

The long and short of it is, that if you take a unit of e.g. 10 identical 1st level warriors, they have an AC equal to a single creature's AC, 10 little boxes of hit points (not really tracked individually, just crossing off half a box or a box or whatever an attack on them rounds off to). So if someone does 15 points of damage to a unit of 10 hp warriors, I'd cross off one and a half of the little boxes.

Then the squad gets one set of attacks, but they are at +1/2*N to hit (where N is the number of creatures in the squad) and +N to damage. So a 10 person squad of 1st level warriors with a a to-hit of +3 and damage of 1d8+2 becomes one creature with an attack of +8 and damage of 1d8+12. See Quickie Mass Combat Rules for more details. I've used this in play for a long time and it works well.

Pros:

• Reduces die rolling by a huge amount
• Works seamlessly with larger scale combat - my PCs have a pirate ship full of pirates, so it's often them plus 3 units of pirates vs. a bunch of units and a couple higher level NPCs aboard an enemy ship
• it makes threats more credible without being overwhelming. I had one player who figured "Oh, I'm 7th level, I can totally take on that entire shipful of Chelish marines single handed" have to be airlifted out because they could actually hit his ridiculous AC and do some meaningful damage in numbers.

Cons:

• You have to make judgement calls about mass-damage effects and area effects and stuff like that which shouldn't affect just one person in the unit but also not all of them. I get along fine just SWAGging it. "Web? OK, roll d10 and that's how many of them you catch in it."

Answer 3

Environmental factors

Perhaps incorporate some environmental features that will balance the encounter in the favor of the cave spiders.

For example, in your instance with the cave spiders, spiders are typically always found surrounded by spider webs that only they can walk on, so fill rooms full of the spiders with webs that the players have to roll saves or skill checks to navigate through (as if affected by a web spell).

Because the webs are everywhere in the room, assess a penalty or even deny the players their Dexterity bonuses to AC, because dodging an attack when surrounded by webs would likely get them stuck in.. webs. When you describe the webs describe them as "Arm-wide fibers too thick to cut through with a weapon, that would hold fast a sword if it touched the stringy silk."

Upgrading monster statistics

If you have a set of monsters that you roll on an encounter table and it seems like they are unable to hit the PCs due to optimization or inflated armor classes, buff the monsters up a few hit dice.

For each new HD you decide to add, roll another 1-3 HP dice per monster, and increase their base attack bonus for each hit dice depending on their monster type and its BAB progression. (This is normally found in the back of the Monster Manuals under creature types.)

Roll twice

Have an encounter in an area include more than one roll of the encounter table for that CR if the monster seem too weak. Those spiders may look a little more dangerous when surrounded by webs and accompanied by a Drider. I am not saying that a Drider would be on the same location of the table as a bunch of cave spiders, but it wouldn't be uncommon to find them together.

Answer 4

If you want a simple, RaW way to up to to hit, saves and AC of randomly generated monsters, have you considered spells?

Those spiders might be there randomly, or they could have been sent by a Drow raiding party. who cast Mage Armour and Bull's Strength on them before sending them off to do their master's bidding.

Might start to seem unbelievable if you do it too often on too many different monsters, but should see you through a few sessions if the random creature generator only sometimes returns hordes of low level monsters.