The Premise
Me and a few others decided to hold this game's feet to the fire and see if this stuff really works: the "challenge rating" guidelines from the Monster Manual and the "adventuring day" guidelines from the Dungeon Master's Guide.
For those unaware, Challenge Rating is defined the Monster Manual as:
An appropriately equipped and well-rested party of four adventurers should be able to defeat a monster that has a challenge rating equal to its level without suffering any deaths. For example, a party of four 3rd-level characters should find a monster with a challenge rating of 3 to be a worthy challenge, but not a deadly one.
And the adventuring day guidelines from the Dungeon Master's Guide:
Assuming typical adventuring conditions and average luck, most adventuring parties can handle about six to eight medium or hard encounters in a day. If the adventure has more easy encounters, the adventurers can get through more. If it has more deadly encounters, they can handle fewer.
and
In general, over the course of a full adventuring day, the party will likely need to take two short rests, about one-third and two-thirds of the way through the day.
We also keep in mind the “Adjusting XP for multiple monsters” guidelines from the DMG.
The Party
The characters chosen for this endeavor were intended to be the most classic characters, and ones that will perform the most consistently in each encounter.
Hill Dwarf Fighter: Champion
Lightfoot Halfling Rogue: Thief
High Elf Wizard: School of Evocation
Human Cleric: Life Domain
Not going to go into too much detail about the classes but you can assume we picked the most "basic" and strongest spells and options. I.e., Wizard had Magic Missile, Shield, Sleep, Misty Step, Fireball, etc. and Cleric had Bless, Healing Word, Spiritual Weapon, Spirit Guardians, etc.
No feats, no multiclassing, and no magic items outside of basic +X weapons and armor and potions of healing. We gave ourselves little treasure "hoards" using the Tiers of Play as a guideline from the Dungeon Master's Guide. 500 gp plus 1d10 × 25 gp, one uncommon magic item, normal starting equipment at 5th level; 5,000 gp plus 1d10 × 250 gp, three uncommon magic items, one rare item, normal starting equipment at 11th level; and 20,000 gp plus 1d10 × 250 gp, three uncommon magic items, two rare items, one very rare item, normal starting equipment at 17th level.
The fights all took place in a vacuum 20x20 (or 100 ft by 100 ft) room with both parties rolling initiative about 40 ft apart from the other. We let our characters be surprised if an enemy's "passive" Stealth was higher than our individual characters' passive Perceptions. We just assumed our party wouldn't really surprise anyone because of our two heavy armor wearers and the Cleric always having Light up.
Challenge Rating 4
Encounter 1: One Flameskull
Wizard loudly announces he casts Mage Armor as soon as wakes up and before we enter the theoretical dungeon to fight this thing. DM says “okay, now make a Dexterity saving throw” as the party takes their first Fireball. Fighter and Cleric fail but both stay up, even after taking 33 fire damage to the face. Flameskull is low so the Wizard casts Magic Missile. Flameskull Shields. Flameskull throws a Magic Missile back at the Wizard who now goes to 0. Cleric picks him up, and Rogue finishes the Flameskull off.
Encounter 2: One Lamia
Honestly kind of underwhelming? The Fighter and Cleric had too much AC for this thing to hit them with much. Fight only lasted 3 rounds so it never really got to do anything with the Intoxicating Touch. Party opts to short rest just because they’re missing hit points but otherwise nobody feels like they’re dying.
Encounter 3: Gnoll Fang of Yeenoughu
Cleric got downed, then used its Rampage to go after the Wizard, but was otherwise dealt with without much worry. Cleric starts next fight at 1 hp.
Encounter 4: Three Specters
Specters win initiative and fuck up the Wizard and Rogue. Cleric dodges the hit. Cleric tries to Turn Undead knowing these fuckers can suck our max HP. They all fail so the party starts preparing and then the Rogue takes a shot, which the Specter resists the non-magical attack, then it immediately attacks the Wizard again. Wizard Shields. Other two Specters fly away and we ready up for their return. Basically everyone avoids getting hit or casts Shield because we don’t want to risk the max HP reduction. Surprisingly not too hard but we do take our last short rest.
Encounter 5: Two Mimics
We are surprised, except for the Rogue. Wizard casts Web, they both get stuck. They break out, but we are far enough away it’s a sad fight and they both just get kited until they die.
Encounter 6: Two Lizardfolk, One Lizardfolk Shaman
Wizard casts Web, they all succeed the first roll. One gets grabbed when he starts his turn, the other only has enough movement to get to the Fighter, much to the Fighter’s delight. Everyone is expecting an easy win now. Shaman is restrained by Web, but casts Conjure Animals and summons eight velociraptors, which roll initiative at the top of the round. This fight has just changed dramatically.
Fighter decides to Dash with his action, and takes seven opportunity attacks in the process. Runs to the Shaman, and Action Surges, and kills the Shaman, and the raptors disappear. We clean up the remaining lizardfolk and we all agree Fighter was the hero of that fight. Wizard and Cleric say they have enough spell slots they could probably do one more fight so we press on.
Encounter 7: 10 Blink Dogs
Dogs surprise everyone but the Rogue, again. They teleport to us and start biting. By some miracle they miss most of their attacks. This was probably the most boring fight we’ve had. It was like 11 rounds of just attack, miss, magic missile, sneak attack, repeat. Fighter went down once but after one healing word he never did again.
Conclusion
Nobody died, and almost nobody went down despite the party getting our first fireball to the face. Wizard started doing a lot more. I really don’t have much to say about this except every encounter was either “holy shit, it’s go time” or just a slog. The Flameskull and the Lizardfolk were scary but almost everything else it was like routine to deal with them. Web seems a bit too good, much like back when we did CR 1 and Sleep was too good. What I can say though is everyone was so fucking important. The Rogue’s consistent damage, the Fighter’s AC and action surge, the Cleric’s healing, the Wizard’s area control. Everyone was doing their part so fucking well this time. Like the necessary teamwork was really starting to show at this point. Otherwise I think we can confirm that Challenge Rating and Adventuring Days works up to 4th level.