D&D 5E Let’s Read Mordenkainen Presents: Monsters of the Multiverse.

[Paul Farquhar]

CR would be more useful if you split up the numbers into Offence Rating and Defense Rating. But even then its only a measure of DPR.
To get a better read on now deadly a monster is, you would need to take into account its Mobility, Range, Action Economy, and Special Win Conditions.

For Speed there are really only three numbers you need to consider:
Anything below 30 speed without a ranged attack and/or a movement ability is a chump. A DM is going to have to compensate for slow monsters like these.
40' speed is the bare minimum I would recommend for a melee-only monster. Humanoids can be slower, but most humanoids can also wield ranged weapons or spells to compensate.
With 60' or more of speed, a monster can render short range attacks useless, which happens to be the bulk of ranged attacks. Mounted combatants can easily reach this speed, which is why horses are so dangerous in combat.

The rest of Speed concerns special movement types. Does the creature have any of them? If so, they are more deadly. In most cases, when given an appropriate environment, there isn't a functional difference between Climbing, Swimming, or Flying, they all add 3d into the combat.
Teleportation is good, but not as good as magical transportation would imply. While you can use it to break out of a trap or grapple, use it as a Disengage, or reposition yourself regardless of interposing obstacles, you are still limited by your other movement types. You can't teleport into the air and expect to survive without a supporting fly speed, for example. And often Teleportation is limited by x number of uses or some other factor (such as only into shadows).
Burrowing, on the other hand, is on a whole other level. It can do the 3D combat, and provide up to total cover for the creature to attack from below. Handily the most dangerous form of movement.

For range, there are 5 basic categories:
15' or less (basically Melee), 20-60 (short), Up to 80' (Mid), Up to 100' (long), 120'+ (Extreme).
Extreme Ranged combat basically turns anything anything Mid Range or lower into pincushions.

Action Economy is "How many Actions can this monster negate, or create." Because CR is calculated by Tank-and-Spank metrics, where the combatants just trade DPR with each other, and the Action Economy functions as a Force Multiplier for DPR. You could go as far as saying that Actions are true currency of combat and DPR is just a tax to play with a given CR.

Special win conditions are things like Stat Damage, or knocking targets Unconscious. Anything that lets them bypass the HP mechanic entirely. These effects completely throw the DPR out the window, and often just kill the PCs outright over the course of a single battle.

Good ideas, but then you have a system which is too complicated for WotC staffers to use, never mind inexperienced DMs. And the more complex and formal a system, the more it looks like hard rules rather than guidelines.

And it still doesn't allow for circumstance.

 

[Paul Farquhar]

Or the under-optimizer who just grabs classic spells. I have a friend who frequently uses sleep even against obviously higher-level foes because she really doesn't bother to look at what each spell does or compare them to other spells, and I always feel so bad when I have to tell her her spell has no effect.

Indeed, it's not like you need obscure spells to beat quicklings. Magic Missile is another one which is highly effective against them.

 

[Sulicius]

Indeed, it's not like you need obscure spells to beat quicklings. Magic Missile is another one which is highly effective against them.

So that’s 2 out of about 30 1st level spells that are solutions. You are not thinking like an average player. They can easily lack the tools to deal with this.

 

[Paul Farquhar]

So that’s 2 out of about 30 1st level spells that are solutions. You are not thinking like an average player. They can easily lack the tools to deal with this.

Sleep, Magic Missile, Mage Armor and Shield are by far the most commonly chosen wizard spells, especially by novice players.

 

[dave2008]

Eh? Evasion doesn't affect AC, and is largely irrelevant when fighting quicklings, since reasonably competent players aren't going to use DEX save spells against them.

Possibly not, I had previously read it as being the same as avoidance (which does provided a +1 to AC), but I see now that it is slightly different.

Evasion. If the quickling is subjected to an effect that allows it to make a Dexterity saving throw to take only half damage, it instead takes no damage if it succeeds on the saving throw, and only half damage if it fails.

Avoidance. If the demilich is subjected to an effect that allows it to make a saving throw to take only half damage, it instead takes no damage if it succeeds on the saving throw, and only half damage if it fails.

Avoidance

Demilich

Increase the monster’s effective AC by 1.

 

[Sulicius]

Sleep, Magic Missile, Mage Armor and Shield are by far the most commonly chosen wizard spells, especially by novice players.

Got data on that? Most players I play with don’t look up the best spells every level.

 

[Paul Farquhar]

Got data on that? Most players I play with don’t look up the best spells every level.

40 years of playing experience? They are not "the best". They are ones that look good to inexperienced players. And, like Fireball, are somewhat inflated because of their "classic" status from 1st edition.

Your power gamer is probably loaded up on Silvery Barbs and Hideous Laughter instead. God wizards don't bother with damage spells.

 

[MonsterEnvy]

Got data on that? Most players I play with don’t look up the best spells every level.

This is not the best spells. But the most commonly picked ones.

 

[FitzTheRuke]

Got data on that? Most players I play with don’t look up the best spells every level.

That's not a list of the best spells. That's a list of the most commonly picked spells. Sleep isn't even all that good. They're just really well known, well loved, and easy to imagine what they do. Nearly every pregen wizard I've seen has them, far or less ones people make for themselves.

 

[Leatherhead]

Rutterkin (MToF)​

Rutterkin are Demons that roam around the Abyss, looking for non-demons intruders to kill. Though at CR 2, they aren’t particularly good at that task. The more interesting thing about Rutterkin is their diseased Bite, which can turn their victims into a Manes, placing them on the lowest rung of the Demonic hierarchy.

That secondary fact could be exploited by evil-doers who are looking to build up a stockpile of Demons for whatever reason. Or it could be used as a “Zombie Horde” scenario. Unfortunately with Demons, there isn’t a whole lot you can do with most of them due to their nature.

In combat, the Rutterkin is also like a zombie: A slow, Ground-Bound, Melee Brute with more resilience than it should have. They do have one interesting feature, a 30’ fear aura that can also restrain, and gets harder to resist if you are fighting a swarm of Rutterkin. The ideal strategy for the Rutterkin is to dash forward, trap someone with the fear, and then pounce upon them in a group, hopefully transforming the victim in the process.

For this book, their Fear aura was changed to trigger from one Rutterkin instead of three minimum, and had its name changed from Crippling Fear to Immobilizing Fear. More interestingly, their Bite attack was changed to convert the victim into a Manes. Previously, the Bite converted the target into a slightly more dangerous monster, the Abyssal Wretch. A CR 1/4 monster that was created for MToF, but omitted from this book.