This might be the only one that I have found that seems to be a straight up nerf. It lost 2 AC, lost any resistance to non-magical weapons, its tail attack is now a save instead of an attack roll and lost 5 feet of range, and the escape DC went down by 5, and all it gained was 12 damage ( was 13 slashing, now 10 slashing and 7 necrotic) and an extra +1 to hit along with +5 passive perception and 31 HP. The only new addition that is truly a big buff is that teleport is now a bonus action. I would way rather have the AC back, and how did its natural AC go down in the first place? 

There is an error - Pact Blade attack bonus listed as +10 - but PB + Str Mod = + 9

I do love the new art

It is using its Charisma for its attacks. Im assuming just like the Warlock invocation Pact of the Blade that allows the same ability, I can only imagine it is being transferred here. As its PB is +5 and its CHA is also +5

Quote from casliber >>

There is an error - Pact Blade attack bonus listed as +10 - but PB + Str Mod = + 9

I do love the new art

 The Marilith is using it's DEX instead of STR 5(dex)+5(pb)=10 this can also be seen in the damage bonus being +5, matching its DEX bonus.

Gbrowniie is correct actually. The attack is a clear reference to the pact of the blade that warlocks have.

And yeah this art is cool, really brings out that idea that demons can look like anything vibe when compared to the 2014 art.

Quote from Gbrowniie >>

It is using its Charisma for its attacks. Im assuming just like the Warlock invocation Pact of the Blade that allows the same ability, I can only imagine it is being transferred here. As its PB is +5 and its CHA is also +5

 Your math is correct but I would argue that the marilith is using it's DEX instead of STR or CHA for their + hit and dmg bonus.

You would be correct, took me a minute to realize that pact blade is a refrence to the pact of the blade.

Quote from theron >>

This might be the only one that I have found that seems to be a straight up nerf. It lost 2 AC, lost any resistance to non-magical weapons, its tail attack is now a save instead of an attack roll and lost 5 feet of range, and the escape DC went down by 5, and all it gained was 12 damage ( was 13 slashing, now 10 slashing and 7 necrotic) and an extra +1 to hit along with +5 passive perception and 31 HP. The only new addition that is truly a big buff is that teleport is now a bonus action. I would way rather have the AC back, and how did its natural AC go down in the first place? 

I would argue that the gained hit points, damage, +1 to hit bonus and the bonus action teleport is more than worth the 2 AC  it lost for not wearing breastplate armor.

The AC is explained by if you compare 2024 artwork to the 2014 artwork you can see that this particular marilith is not wearing breastplate armor for that 16+(2 dex). Instead it is relying on a natural armor bonus of +1 and +5 from dex leading the math to be 10+1(nat armor)+5(dex).

The old one said it was natural armor not breast plate, the art was just for show since the math wouldn't work for breast plate, and honestly +1 hit is not worth losing 2 AC. Thing makes 7 attacks it is going to hit eventually, losing resistance to non-magic weapons can hurt as well but that's universal in this book. However, losing 2 AC in bounded accuracy is nuts. I agree that the bonus action teleport is a huge boost, but 31 HP is just 2 attacks if that at high level, attacks that may not have hit in the first place if you just had the better AC.

Quote from theron >>

The old one said it was natural armor not breast plate, the art was just for show since the math wouldn't work for breast plate, and honestly +1 hit is not worth losing 2 AC. Thing makes 7 attacks it is going to hit eventually, losing resistance to non-magic weapons can hurt as well but that's universal in this book. However, losing 2 AC in bounded accuracy is nuts. I agree that the bonus action teleport is a huge boost, but 31 HP is just 2 attacks if that at high level, attacks that may not have hit in the first place if you just had the better AC.

 Aaa true. it did say it was natural armor now that i went and checked, good catch. I also misremembered the breastplate being 16+max 2 (dex). Quess the new marilith just lost +2 natural armor for some reason.

But I will still hold that with the teleport and the potential dmg boost it slightly stronger than the old one.

Quote from Gbrowniie >>

It is using its Charisma for its attacks. Im assuming just like the Warlock invocation Pact of the Blade that allows the same ability, I can only imagine it is being transferred here. As its PB is +5 and its CHA is also +5

 Epic fail on my part - well spotted!

Given the increases to the Marilith's damage output (shorthand of bonus to hit and average damage) and hit points, the AC has to be reduced to keep the Marilith a CR 16 monster. A reduction of 2 is just what is necessary to do that.

Quote from TheOtherRyan >>

Given the increases to the Marilith's damage output (shorthand of bonus to hit and average damage) and hit points, the AC has to be reduced to keep the Marilith a CR 16 monster. A reduction of 2 is just what is necessary to do that.

 How do you figure? Not trying to pick a fight just curious as to how you are doing the math for that. CR12 archmage does 104 damage a round, CR16 marilith does 117 a round if they fail saving throw. Archmage has base AC of 17 + shield so effectively 22 AC, Marilith has base AC of 16 + Parry which is only for melee and not every attack. Why is only 13 extra damage worth having a lower AC when Marilith is 4CR higher???

Quote from theron >>

Quote from TheOtherRyan >>

Given the increases to the Marilith's damage output (shorthand of bonus to hit and average damage) and hit points, the AC has to be reduced to keep the Marilith a CR 16 monster. A reduction of 2 is just what is necessary to do that.

 How do you figure? Not trying to pick a fight just curious as to how you are doing the math for that. CR12 archmage does 104 damage a round, CR16 marilith does 117 a round if they fail saving throw. Archmage has base AC of 17 + shield so effectively 22 AC, Marilith has base AC of 16 + Parry which is only for melee and not every attack. Why is only 13 extra damage worth having a lower AC when Marilith is 4CR higher???

 You're not picking a fight by asking someone to elaborate or explain themselves. I am happy to.

The key differences, beyond what you have already mentioned, is the fact that the Marilith can survive more rounds and thus inflict more damage to parties. The Marilith has resistance to cold, fire, and lightning damage, like all demons. The Marilith also has immunity to poison damage and the poisoned condition. Further, the Marilith can use Parry each turn that it is targeted by a melee attack, while the Archmage can use shield three times (and must forego counterspell to do so). Even if the Archmage uses Multiattack to deal the maximum amount of damage it can each turn, then the Marilith will still deal more damage, as you noted. There are also other factors, like the Marilith's true sight, which prevents creature from utilizing invisibility or magical darkness against the Marilith. The Marilith also has 50 more hit points than the Archmage. These reasons are why the Marilith is a higher CR than the Archmage.

With an AC of 18 (making the AC after parry equal to 23), the Marilith is too powerful for a CR 16 creature. AC is roughly interchangeable with more health (though this is an oversimplification). But to summarize, having two additional AC means that the Marilith will be hit 10% less, which roughly equates to a 10% increase in hit points (not exactly true because when the AC nears or exceeds 20 the benefits of additional AC are greater, and missing can be more punitive than simply saving the monster hit points because it prevents effects that trigger on a hit from applying). So that amounts to approximately an additional 22 hit points (on average). But, in total, a Marilith (with all the aforementioned features) with an average of 242 hit points is beyond CR 16.

Another thing is that the Marilith has a better action economy than the Archmage (though the Archmage having four Arcane Bursts via Multiattack is helpful), allowing the Marilith to spread damage out more easily than the Archmage.

Let me know if this answers your question.

Thank you for explaining. I agree with the action economy and the resistances, but I think your interpretation of parry is somewhat skewed. In 2014 I would have agreed with you, but with how dual wielding and TWF works, many martials will make 4+ attacks per turn, so parry only blocking 1 of 4 means less blocked attacks then just having the +2 AC and no parry at all. In addition, this has the lowest base HP of all CR16, and aside from dragons who are flying and therefore much more complicated to calculate, the Marilith has 40 less HP than the other CR16 monsters. On top of that parry only works on melee, so if the party has 1 caster and 3 melee martials, the AC balance gets even worse. The other CR16s all have either 19 or 20 AC permanently aside from the githyanki who is 18, and several of them fly on top of that. I suppose the new marilith is meant to be a glass cannon, with niche melee defenses, but if that were the case it really needs a bit more damage to balance that out. Archmage is also meant as a glass cannon, and it having comparable damage while being 4 CR lower is not a great look, nor is the Death Knight who is a CR17 glass cannon and far out damages the Marilith doing 150 damage a round.

Gulthias Blight is AC 20 and 264 HP with 64 damage, but it has a ranged attack and also can heal for 14HP a round possibly stacking both healing and increasing in damage in subsequent rounds making its effective HP much higher. Iron Golem is AC 20, 252 HP, 3 immunities and the ability to potentially heal, as well as 72 damage per round and potentially 165+ damage on round one and repeating on a recharge. These all have a permanent AC of 20, so the Marilith having only 16 AC and an incredibly niche way to bring it to 21 against 1 attack per turn, and only if its melee, is mathematically weaker than just having 18 AC and no parry. And offensively the lack of a ranged option makes it very limited in its offensive capabilities for a CR16, especially as it cannot fly either. This Marilith is far from being weak, but it feels very fragile especially if the teleport doesn't recharge quickly and with no flight or range it is an incredibly niche CR16 for this new MM. Obviously we have had the debate before on several pages, but again this conversation is an example of why having the formula WOTC used to determine CR would be useful. 

We won't know until we have had time to really playtest them, but on paper with the way TWF and Dual Wielder works now parry just seems so much less useful than it was. I will remain cautiously optimistic on it for now.

Quote from theron >>

Thank you for explaining. I agree with the action economy and the resistances, but I think your interpretation of parry is somewhat skewed. In 2014 I would have agreed with you, but with how dual wielding and TWF works, many martials will make 4+ attacks per turn, so parry only blocking 1 of 4 means less blocked attacks then just having the +2 AC and no parry at all. In addition, this has the lowest base HP of all CR16, and aside from dragons who are flying and therefore much more complicated to calculate, the Marilith has 40 less HP than the other CR16 monsters. On top of that parry only works on melee, so if the party has 1 caster and 3 melee martials, the AC balance gets even worse. The other CR16s all have either 19 or 20 AC permanently aside from the githyanki who is 18, and several of them fly on top of that. I suppose the new marilith is meant to be a glass cannon, with niche melee defenses, but if that were the case it really needs a bit more damage to balance that out. Archmage is also meant as a glass cannon, and it having comparable damage while being 4 CR lower is not a great look, nor is the Death Knight who is a CR17 glass cannon and far out damages the Marilith doing 150 damage a round.

Gulthias Blight is AC 20 and 264 HP with 64 damage, but it has a ranged attack and also can heal for 14HP a round possibly stacking both healing and increasing in damage in subsequent rounds making its effective HP much higher. Iron Golem is AC 20, 252 HP, 3 immunities and the ability to potentially heal, as well as 72 damage per round and potentially 165+ damage on round one and repeating on a recharge. These all have a permanent AC of 20, so the Marilith having only 16 AC and an incredibly niche way to bring it to 21 against 1 attack per turn, and only if its melee, is mathematically weaker than just having 18 AC and no parry. And offensively the lack of a ranged option makes it very limited in its offensive capabilities for a CR16, especially as it cannot fly either. This Marilith is far from being weak, but it feels very fragile especially if the teleport doesn't recharge quickly and with no flight or range it is an incredibly niche CR16 for this new MM. Obviously we have had the debate before on several pages, but again this conversation is an example of why having the formula WOTC used to determine CR would be useful. 

We won't know until we have had time to really playtest them, but on paper with the way TWF and Dual Wielder works now parry just seems so much less useful than it was. I will remain cautiously optimistic on it for now.

 It’s totally fair to look at the diversity of CR 16 monsters and wonder what went into assigning that challenge rating. Challenge Rating is a complex calculation that is influenced by many factors that defy numerical evaluation, but it’s not arbitrary. 

To review, Moderate Difficulty is described as follows:

• Moderate Difficulty. Absent healing and other resources, an encounter of moderate difficulty could go badly for the adventurers. Weaker characters might get taken out of the fight, and there’s a slim chance that one or more characters might die.

Challenge ratings represent ranges of difficulty. Any monster encounter that is a Moderate Difficulty encounter for a group of four characters has a challenge rating equal to the average level of that party’. That’s why diverse monsters with extremely different features, abilities, and scores can nonetheless share the same challenge rating. It’s natural that the weakest CR 16 monster should present a similar threat to the strongest CR 15 monster (and vice versa). That’s simply the nature of these sorts of measurements.

I think you’re focusing too closely on the Marilith’s ability to Parry. Challenge Rating is not modular, so comparing individual numerical features of a stat block in insolation is a fundamentally ineffective method of identifying the relative difficulties of monsters. The points you bring up are in fact true! Parry is by definition weaker than Shield, but that numerical difference is not what matters. What matters is what the average level of a group that encounters a Marilith at Moderate Difficulty. The same holds true for hit points. It’s not the number themselves that’s important, it’s the number in relation to the monster’s other traits, abilities, and features that together determine what average level of groups fight the monster at a Moderate Difficulty.

I’m almost hesitant to mention this, but when I first started playing my DM explained that when he chose a monster for us to fight he never went above a challenge rating equal to the party’s level plus our proficiency bonus. I don’t think that’s a good rule for a number of reasons, but it illustrates the general concept of what I’m getting at. Challenge Rating is a rule of thumb, not the precise, scientific calculation that many hope and expect it to be. The more challenge ratings that you go above your party’s average level, the harder it will be for them to defeat that monster.

You can say, “But if WOTC can calculate CR, then I should be able to as well.” I disagree. I won’t go into why as, like you said, I have already in other places. But the bottom line is that individual DMs cannot truly calculate CR because we cannot access the information necessary to do so. CR represents what the difficulty against average party of a given level. What matters for individual DMs are our groups. A DM with two clerics, a paladin, and a necromancer wizard will deal with a Wraith far more easily than two fighters, a rogue, and ranger. But if you’re designing monsters without a specific group in mind, then you’re best off comparing your creation to monsters of the desired CR. That way, you’ll gain the benefit of WOTC’s CR assessments and stay with a range of difficulties appropriate for the intended level.

Ultimately, I agree that the proof is in the pudding: we will see how well these designations hold up over time. But you imply that these challenge ratings are guesses, and that is incorrect. The challenge ratings of (pre-existing) monsters in this MM are in fact the same as in the previous MM (sans a small number of exceptions). WOTC has used the enormous volume of data gathered throughout all of 5e to change each monster’s stat block to be more in line with its challenge rating. On top of that, WOTC play tested each monster (and all their iterations) extensively prior to release. So, WOTC presents these monsters atop a mountain of research and play testing.

To finish off on the Marilith, I would describe it as this: the monster got stronger, so WOTC made something about it weaker to not disturb its overall power level. Let me know if this answers your question.

It also has a +10 bonus to initiative which is really good for it.

When comparing this creature to something like the Archmage, it is also worth taking into account the subtler features of its statblock. For instance, the marilith has truesight out to 120 ft, which I think is quite powerful, especially when dealing with spellcasters. Also worth noting is its 120 foot bonus action teleport that, while on a recharge, is a massive mobility boost.

I've got a bone to pick here. 

Initiative +10 and the bonus action teleport are both good changes; supernatural reflexes and being able to warp next to the casters AND maul them in a single turn. Cooldown on the teleport is fine, given that it's now a bonus action instead of a regular one.

16 AC is low, especially with how much stronger 2024 player characters are; old chart recommends 18 AC and level 12s on average have +9 to hit before buffs. 3 hit dice are nothing compared to losing physical resistances. DCs on Constrict are much lower; 17 save & 14 escape check are poor when compared to the old 10 foot reach attack and DC 19 escape (really should be 17 if scaling w/ Str); lack of reach also means that it's easier to just push or pull the grappled character out of the marilith's reach, ending the grappled and restrained conditions prematurely.

1d10 physical damage from a large creature's weapon is a flavor failure; what 1-handed melee weapon uses a d10, and why is it not 2d8 or 2d6 from appropriately sized weapons? The added necrotic damage makes some sense, given how high-level blade pact warlocks work, but that doesn't impact the inconsistent nonsense.

If the issue is that it does borderline CR 19 levels of damage (117-122), I'm sure we can agree that WotC overcorrected with the defense nerf (AC 16 is expected of CR 8-9!). Toning the DPR down to about 103 should be enough to warrant raising its AC back up. Without survivability, it'll likely die in 1 or 2 rounds against a tier 3 party, which would be somewhat anticlimactic.

ive alwatys struggled with describing the demon's teleportation ability. Any advice?

I'm a simple man. 2014 Marilith looks and feels better.

Can't even really see the art. They covered up most of it with suits of armor. It doesn't even look like it has a snake body.

Am I the only one who prefers the old art of the sexy snake lady? Although this art promotes the fighting prowess of this creature, the previous art showed how a demon could use its looks and charm to achieve its goals.