“Challenge Ratings” are one of the basic elements of the d20 system; they’re built into it’s assumptions about combat, level advancement, and treasure. Given how fundamental they are, it’s rather troubling, if no surprise, to note that they never have worked very well.
The definition is pretty simple: “The average level of a party of adventurers for which one creature (of this type) would make an encounter of moderate difficulty”.
An “encounter of moderate difficulty” is defined as one that the player characters should win handily at the cost of using up about 20% of their resources – hit points, spells, magic item uses, and so on – in doing so. Straightforward enough, at least if you disregard that this says that – if a character has a fully-charged Wand of Fireballs – it should be used at least ten times during such an encounter, that – since near-limitless out-of-combat healing is fairly easy to get – any hit point loss short of death is irrelevant, and that this pretty much decrees that anything except a straight combat encounter is irrelevant. That even discourages more complex combat goals; how often do you see things like “silently”, or “capture alive”, or “don’t set off the magic-sensing alarms”, or “we want to leave them alive and blaming someone else”, or “don’t give them a chance to destroy the papers they’re carrying or use area effects that might do it yourselves”, or “rescue the extremely vulnerable hostages”, or “protect the ritualists while they work”, or “get some barriers up and the doors closed to keep their reinforcements out”, or “do not hurt the possessed child”, or “grab the target and escape, without trying to fight the overpowering foe”, or even “we want to leave them with no memory or evidence of anything except having briefly dosed off” (a popular goal in espionage settings) come up?
Thus a classical “Challenge Rating” for a creature mostly comes down to “how menacing is it in a straightforward fight?” – and that tends to be more-or-less guesswork to start with. After all, even if you used some sort of standard party and encounter setup to determine challenge ratings, how can you enforce a standardized level of optimization, average tactics, and a generic “white room” encounter setup, on everyone out there who’s actually playing?
Once circumstances and parties start getting even a little odd – Cage Match in Dead Magic Zone! Iron Golem in a Room Seething with Magical Fire! Party members all laboring under the effects of two or three curses each from that evil high priest in the last room! “Thieves Guild” Party of Rogues and Bards with a token Ranger! Party of Heavily Optimized Clerics and Druids! The Goal is to convince the Princess to marry you without leaving traces of magic or psionics on her, not to kill her! Magic of above third level doesn’t work in the setting! Monsters are being unusually clever or stupid! Players are tactically skilled or terribly inept! – “Challenge Rating” ceases to be worth much even as a guide.
I once had a player who possessed such bad luck, and such a dire anti-genius for tactics and plans, that I gave him a 12’th level cleric to play when the rest of the party was level four. That made his character just barely worth having along – although (usually after some especially spectacular failure) the other players occasionally discussed abandoning their disaster-prone priest when the player wasn’t around. Still, for good or ill, they pretty much always decided that having someone around with access to healing magic that powerful was worth putting up with the disastrous decision-making.
There are just too many variables in d20 games to really assign fixed challenge ratings to particular creatures. Even in Eclipse, where you can calculate precise costs, you can’t really account for playing skill, character (or creature), optimization, spell exploits, tactics, and circumstances.
Fortunately, there is another way – in fact, a fairly classic one.
When designing an encounter forget the “challenge ratings” in the books and just eyeball it. You should know your party and players tolerably well; set it up to make it interesting, gauge the challenge rating afterwards, and then hand out appropriate treasure. Was the opposition using more equipment than that in the fight? Well, it was limited-use boosters that are now used up, personal powers that made normal items act like they were magic, and other stuff that the players cannot readily turn into loot. As for determining the actual challenge ratings to calculate that experience and treasure…
- If the players breezed through your encounter trivially, it wasn’t worth experience. It doesn’t matter if it was a battle with a god; if your uber-charger went first and wiped it out with his or her initial charge… well, it’s pretty obvious that it was not a worthwhile challenge. There might be a little treasure around, but it’s going to be small change.
- If the players handled it readily, but did have to work a bit and spend a reasonable chunk of their resources, the challenge rating was (their average level – 2).
- If the players had to work hard to win, and spent a good chunk of their daily resources doing it, then the challenge rating was (their average level).
- If it was a really serious struggle, casualties were likely, and they spent a BIG chunk of their daily resources, then the challenge rating was (their average level + 2).
- If it was a horrific “boss battle”, the players had to give it everything they had, and a total party kill looked possible, then the challenge rating was (their average level + 4).
Now for some modifiers…
- If the players employed scouting, planning, sensible tactics, and preparations to make what would have been a hard battle easier, raise the final effective CR by +1 with a minimum of (the groups average level – 2).
- If the players were outright brilliant, and thus made it look easy, raise the final effective CR by +2, with a minimum of (the groups average level).
- If one of the players had a stroke of genius that awed the entire table, and so managed to turn what SHOULD have been a tough encounter into a cakewalk… raise the final effective CR by +4, with a minimum of (the groups average level +2).
- If a player character died heroically during the encounter, raise the final effective CR by +1.
- If you wish to encourage stealth and negotiation, be sure to award experience for bypassing creatures or dealing with them by persuasion to reach other goals. Optionally, add +1 to the final CR if the group restrained themselves to keep the death and violence to a minimum.
Now the basic system is slanted towards slightly slower-than-usual advancement, but if you want to change that, just add +1 to the final CR’s.
So why SHOULD a groups “experience points” depend on how much trouble they had dealing with an opponent? Is it just that hard fights are more of a learning experience? Why should that affect the amount of treasure?
Well, if you need to justify it beyond “it keeps the game working”, remember… “Experience Points” have nothing to do with actual learning. I’ve studied a lot of things, and I’ve had a lot of experiences – and none of them have suddenly allowed me to learn a new language, or to pick up the ability to cast spells, or abruptly become an expert in a field, or any of the other things that gaining experience does for a character. Looking at what “experience points” actually do in the setting, “experience” is pretty obviously a form of magical energy that accumulates in people and items under various circumstances – mostly during combat – and transforms them when it reaches various thresholds.
So you dealt with a situation too quickly and easily to properly release (or perhaps generate?) that power or to absorb it properly? Then you don’t get much (or perhaps any) “experience” – and the energies that you thus wasted flooded out into the world and into your opponents equipment uncontrolled.
And uncontrolled, random, transformations are far more likely to turn valuable items into junk than vice-versa.
As a side benefit, that bit of metaphysics explains why encounters of lower CR’s provide progressively less experience; a high-level character is already too highly charged to absorb any more from such a weak source; if anything, the flow tends to be the other way – thus any really weak creatures that survive an encounter with a high-level opponent are likely to find themselves filled with “experience points”, even if they only managed a fighting withdrawal.
- Skin of Stone, Man of Straw; Encounters Beneath the Eclipse. (ruscumag.wordpress.com)
- D20 Failure Modes, Part I (ruscumag.wordpress.com)
- d20 Failure Modes VIII – The Apollo Mission and the Old School (ruscumag.wordpress.com)
- d20 Failure Modes V – The Nova Strike (ruscumag.wordpress.com)
- [Emergence Campaign] D20 Failure Modes, Part II — Eliminating Rocket Tag (ruscumag.wordpress.com)