The Boston Diaries

The ongoing saga of a programmer who doesn't live in Boston, nor does he even like Boston, but yet named his weblog/journal “The Boston Diaries.”

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Sunday, August 15, 2021

The Dungeons and Dragons 5th Edition Challenge Rating system is deranged

I've been running a D&D5 game for two years and I've yet to come to grips with the “Challenge Rating” system for monsters. There have been times when what I think is a balanced encounter is one sided with the players going “Okay, that must have been the minion—where's the actual boss monster?” and other times when I throw something that should end with a total party kill, but instead is just a “challenging” encounter the party survives.

I think the theory is that a group of four players of level N should be equally matched with one monster of a challenge rating of N. And I read “equally matched” as “a 50/50 chance for either side to be killed.” Whether that's a good reading of the term “equally matched” is debatable, but that's how I'm initially reading it. It makes sense to me—if you have two combatents (and let's face it—D&D involves a lot of combat) of equal skills and equipment, then it should be a 50/50 toss up for the winner. And in plenty of spots in the various D&D tomes I read that four level 1 characters should be an equal match to one CR1 monster.

So I wrote a simulation to test that out. I have four level 1 characters that are pitted against one CR1 monster for 10,000 simulated fights. For the four players, I used the four archetypal types—a cleric, fighter, thief and wizard. For the sake of simplicity, all four will always “run up” to the monster and fight—no ranged attacks are done. I know this isn't completely realistic, but for a “proof-of-concept” it should be good enough.

Anyway, our poor unfortunate victims:

The Cleric
Has an an AC of 14, 1d8+2 HP, no initiative bonus, +1 to attacks, and will do 1d8+1 worth of damage if the attack hits. The Cleric will not attempt to heal any damaged comrades as I don't expect the enounters to last long enough for that to matter.
The Fighter
Has an AC of 16, 1d10+2 HP, +2 to intiative, +2 to attacks, and will do 1d8+2 worth of damage.
The Thief
Has an AC of 13, 1d8+1 HP, +2 to intiative, +2 to attacks, and because of the strategy of the other players (“run up and hit”) the Thief can use their “Sneak Attack” feature to do an addtional 1d6 worth of damage, on top of the 1d4+2 of damage normally done (here, the Thief will always use a dagger).
The Wizard
Has an AC of 10, 1d6 of HP, +2 to intiative and no bonuses to attacks. Normally, wizards would be in the back of the party doing ranged attacks, but because I didn't want the complication of ranged attacks, the Wizard is right up front and close. But I do allow the Wizard the use of two Magic Missiles (the maximum allowed for that spell, which always hit) for the first two rounds (each doing 3d4+3 damage), then Fire Bolt (which does 1d10, but doesn't always hit).

These are pretty bog-standard 1ST level characters. I then went through picking out a few CR1 monsters to throw against the party. The unfortunate enemy victims include:

Animated Armor
Has an AC of 18, 6d8+6 HP, no initiative bonus, +4 to attacks, and does do two attacks of 1d6+2 of damage.
Has an AC of 16, 5d8+5 HP, +2 to initiative, +4 to hit, doing 2d8+2 worth of damage.
Goblin Boss
Has an AC of 17, 6d6 HP, +2 to initiative, +4 to attack, and gets two attacks, the second of which is at disadvantage both of which do 1d6+2 worth of damage.
Half Orge
Has an AC of 12, 4d10+8 HP, no intiative bonus, +5 to attack, which does 2d10+3 damage.
Has an AC of 12, +2 to intiative, +5 to attack, and does 1d8+3 worth of damage.

And because it wouldn't be D&D without the dragons, there's one dragon at CR1—the Brass Dragon Wyrmling (a baby brass dragon):

Brass Dragon Wyrmling
Has an AC of 16, 3d8+3 HP, no initiative bonus, a +4 to attacks which does 1d10+2 damage, or a breath weapon which can do 4d6 worth of damage if the victim can't jump out of the way (but only has a 1 in 3 chance of regaining per round of combat).

For the Brass Dragon Wyrmling, I decided to have it lead with its breath weapon always, and prefer the use of its breath weapon when it recharges, but if not, do a normal attack.

It's not every CR1 monster, but I think it's a decent list to start with, and it should give me a feeling for how this “Challenge Rating” system is supposed to work.

On with the simulation!

10,000 battles between a 1ST level party and some CR1 monsters
monster TPK% #rounds #lived
Animated Armor 28.23 4 2
Brass Dragon Wyrmling 0.36 3 3
Bugbear 4.81 3 3
Gobin Boss 1.18 3 3
Half Orge 2.56 3 3
Lion 0.72 3 3

Well … [Deep subject. —Editor] I'm not sure what to make of the results. Either the simulation is crap, or the whole “Challenge Rating” system is crap. I've heard that it tends to break down at the higher levels, but even here, it doesn't seem to work. A baby brass dragon is less dangerous than a lion? An empty shell of armor is the most dangerous monster? What?

Okay, about those columns—the TPK column is the percentage time the entire party was wiped out by the encounter. The last column is if the party killed the monster, on average, now many party members were left standing? (rounded to the nearest whole value)

So then I decided to throw some other monsters into the mix. And in keeping with the “dragon” portion of D&D, I found a dragon of CR2, CR3 and CR4 (and used the same strategy I used for the Brass Dragon Wyrmling—leading with the breath weapon). And because I'm just mean, I decided to throw in one of the weakest creatures of D&D into the mix—a single kobold. Behold:

10,000 battles between a 1ST level party and some non-CR1 monsters
monster TPK% #rounds #lived CR
Kobold 0.00 2 4
Black Dragon Wyrmling 27.83 4 2 2
Blue Dragon Wyrmling 71.86 6 1 3
Red Dragon Wyrmling 98.36 6 0 4

To be fair, there is a chance for one party member to be killed by the kobold, as the actual average for the number of party members surviving is 3.93—a single kobold is not a complete cakewalk. And there's a slightly better than 1% chance of killing a baby red dragon as a 1ST level party (better than I expected). But somehow, it still feels wrong that some animated armor is still a bit more dangerous than a black baby dragon.

I guess I'll just have to throw my group (a mix of 5TH to 7TH level characters) in front of an ancient red dragon and see what happens … oh wait, did I mention that out loud?

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