The molydeus is a demon of extraordinary power, on par with several named demon princes. The flavor text refers to various demon lords as “masters” of molydei, but there aren’t too many entities to which that word could apply, given that demons are chaotic evil and therefore not likely to take orders from anything less powerful than themselves.
The Mordenkainen’s Tome of Foes flavor text notwithstanding, unless and until new demon lords are crowned and their stat blocks published, there are only two that could indisputably command the obedience of a molydeus: Demogorgon and Orcus. (Graz’zt and Yeenoghu are only one challenge rating higher than the molydeus; I’m not sure that’s enough of a difference. Baphomet and Fraz-Urb’luu have the same CR as a molydeus, so even if one of them created a molydeus, I think it would tell them to buzz off, if not turn on them immediately.) For some unfathomable reason, I looked at that “CR 21” I don’t know how many times, and my brain processed it as “CR 23.” Yes, any demon lord is powerful enough to command a molydeus. SMH.
For a huge creature, the molydeus is speedy, with a movement speed of 40 feet. Its ability scores are all extraordinary, with Strength first and Constitution second—a brute. While it has Innate Spellcasting, it’s secondary to melee fighting. It has proficiency in four out of six saving throws, but one of the big three—Dexterity—is missing from the list, so in relative terms, this could stretchily be noted as a weakness. But it also has Magic Resistance and three uses of Legendary Resistance per day, so whenever it fails a Dex save . . . it doesn’t fail.
Typically for a demon, the molydeus is resistant to physical damage from nonmagical weapons, cold, fire and lightning and immune to poison; it can’t be blinded, charmed, deafened, frightened, poisoned or stunned. (It can, however, be paralyzed, knocked prone or restrained.) It has a truly bonkers +21 Perception modifier and passive Wisdom (Perception) 31. Player characters trying to sneak up on one, at a minimum, will need pass without trace.
The molydeus has a triple Multiattack: a weapon strike and a bite from each of its two bestial heads. The type of weapon isn’t specified, so you can skin it as you please, as long as the damage it deals is slashing. (The flavor text handwaves that, suggesting that the weapon a molydeus wields depends on which demon lord it serves and includes morningstars and flails. If you give a molydeus of
Orcus Yeenoghu a Demonic Morningstar Flail, I think it ought to do bludgeoning damage.)
Two damage dice is low for a Huge creature; you’d expect three. But Demonic Weapon comes with a nasty rider: When the molydeus rolls a natural 20 while attacking with it, “the target is decapitated and dies if it can’t survive without that head.” Five and a half points of damage is a reasonable tradeoff for a 5 percent chance of a one-hit kill if your opponent has a hit point maximum of 110 or more. [ETA: Some discussion of this figure in the comments. The actual value may be significantly lower.] So let’s say the molydeus uses its Demonic Weapon only against enemies who are that tough. It can tell who is and who isn’t. (What if it’s reskinned as a bludgeoning weapon? Instead of lopping the noggin off, the molydeus smashes it in. “I am crushing your head!”)
Wolf Bite has a shorter reach than the molydeus’s other two attacks (10 feet rather than 15 feet) and doesn’t have any unique effect; it’s just additional damage against foes who get too close. The molydeus won’t bother to use it for opportunity attacks, since Demonic Weapon does more damage. Snakebite does quite a small amount of damage—just one die’s worth—but the damage it deals can’t be healed during combat if the target fails a DC 22 Constitution save, because it’s subtracted from the target’s hit point maximum. If any foe with less than 110 max hp is foolhardy enough to get within reach of it, this is the attack to use against them.
This is all impressive, but it’s not especially interesting. Where the molydeus gets interesting is in the synergy between its legendary actions and its Innate Spellcasting, since one of those legendary actions is Cast a Spell. This allows the molydeus to use its innate spells without having to give up Multiattack on its turn. Whenever it can, it will use those spells to make its melee attacks more potent.
Its at-will spells are dispel magic, polymorph, telekinesis and teleport; it can also cast lightning bolt three times per day.
- Dispel magic: It’s rare that a debuff spell will make it through the molydeus’s other defenses and affect it, so when one does, the molydeus immediately tries to make it go away. Its spellcasting ability is Charisma, with a +7 modifier, so it has a two-thirds chance of snuffing a 4th-level spell, but not one of 5th level or higher. Thus, if it fails to dispel a 4th-level spell on its first try, it tries again on the next combat turn, but if it fails to dispel a higher-level spell, it just accepts it. It also casts dispel magic against any 1st- through 4th-level buff its opponents cast on themselves or on one another, and takes one crack at extinguishing a buff of 5th level or higher.
- Polymorph is cute, but it has two drawbacks: It requires concentration to sustain, and it gives at least 1 hp to its target. If the target of polymorph “dies” as an animal, it just comes back as itself, with however many hit points it had before (RIP your great idea of turning the enemy wizard into a fish), so the only practical application of this spell is to confine an enemy in an undesirable form and keep it there. A better use of the molydeus’s concentration is . . .
- Telekinesis, which it can use to pluck squishy opponents from the enemy’s backline, hoist them into the air and haul them within reach of its jaws. (Since sustaining telekinesis beyond the end of the molydeus’s next turn requires a turn action, it will drop the spell—and the targets—as soon as it must choose between prolonging the spell and Multiattacking.) Or it can magically pick up a half-ton object, if one is handy, and drop it on an enemy or two (see “Improvising Damage” in chapter 8 of the Dungeon Master’s Guide for suggested damage—this is 10d10, at the very least). Seriously, this is way better than turning the cleric into a moth.
- Teleport is the flip side of telekinesis: when those cowardly PCs keep running away, the molydeus can relocate itself (along with any demonic allies in its entourage) directly into their path. However, since this carries a chance of failure even when teleporting to a point within view, the molydeus avoids casting this spell unless it has no other good option available, and it never uses it to teleport to a point it can’t see.
- Lightning bolt is for punishing bad positioning. If three or more opponents make the mistake of forming a straight line with the molydeus itself, it opportunistically fires off one of these.
What about imprisonment? Impractical for combat, because it takes a full minute to cast. However, depending on the demands of your adventure, it’s possible that casting imprisonment is part of a molydeus’s endgame—that its purpose in fighting is not necessarily to kill the PCs, although it does enjoy that, but is specifically to render them unable to stop it from casting imprisonment, on one of them or another target, for the full minute it takes to cast.
When it comes to target selection, the molydeus is shrewd—intelligent enough to size up opponents down to their stat modifiers, prudent enough to recognize if and when they post a meaningful threat to its plans and/or its existence. Despite its Magic Resistance and all its damage resistances and condition immunities, there’s one thing it has no particular defense against: magical weapon attacks, particularly those that deliver radiant, necrotic, force, acid or thunder damage directly, so that it gets no saving throw against them. All it has against these are its Armor Class of 19, and that’s not so big a hurdle to a world-class adventurer. Therefore, opponents with such weapons have to be taken out first and fast.
However, this melee-loving brute is also savvy enough to know that marching right up to an enemy with a +3 holy avenger melee weapon is a dangerously bad idea. This is where the molydeus gets by with a little help from its friends: it commands whatever allies it has on the field to converge on that threat and take it out. It also takes advantage of things they can do that it can’t, such as casting darkness, through which a molydeus can see just fine, over large areas.
In the past, when I’ve examined demon summoning variants, I’ve come to the conclusion that even when the number and type of demonic allies summoned makes it a good bet for the action cost, it may still be better to take a pass on the variant, because both failure and exceptional success (summoning the maximum number of demons) can throw the balance of an encounter way off. Even if you’re the type who doesn’t care about encounter balance, you should care that a molydeus’s losing its entire turn to a failed summoning may well result in its premature demise, disappointing both you and your players. Instead, if you want your demon to summon other demons, you should simply decide that the summoning will work and introduce the new arrivals at whatever moment you find dramatically satisfying.
But that doesn’t mean you can’t introduce a few if-then statements into that formula. For instance, what if a molydeus finds itself facing enemies who can fly? Chasmes can dogfight them. Need something to 1v1 that nuisance with the holy avenger? Send a marilith to do the job.
For that matter, you don’t need to limit yourself to babaus, chasmes and mariliths. Those are merely the types of demons a molydeus can summon. There’s no limit to the types or number it can bring with it. And if it knows who’s coming to mess with it, it selects its team roster accordingly.
A molydeus working solo will handle most conflicts on its own, but there are edge cases. Remember, this is a demon with supernatural Intelligence and Wisdom, not just colossal might. It can size up the opposition in an instant. And if it, by itself, doesn’t constitute a Deadly encounter (see “Creating Combat Encounters,” Dungeon Master’s Guide, chapter 3) for the foes it finds itself up against, it has to make some adjustments, such as summoning enough help to tip the scales (remember, you can simply decide that it succeeds) or using telekinesis to modify the environment to break the problem in front of it into smaller problems. Why fight five or six at a time when you can take them on one or two at a time?
What it will not do, however, is flee. The only thing in the Abyss more powerful than a molydeus is a demon lord. Despite its Wisdom, it’s so cruel, remorseless and destructive that nothing can make it turn away from a fight. It always fights to win, whatever that takes.
So as a basic heuristic, we have Multiattack as the one action that unequivocally makes sense for the molydeus to take on its turn as long as there are foes within reach. What if there aren’t? That may be a good moment to summon some backup—but it can also march juggernautily toward its foes, using the Dodge action as it approaches to impose disadvantage on all attack rolls against it. (This is assuming that its 40-foot speed isn’t enough to bring it within reach of an enemy. If it is, it simply moves, then Multiattacks.)
On other creatures’ turns, it takes legendary actions when those creatures’ actions demand a response. If a melee attacker strikes it, it Attacks back—unless the attacker wields a magic weapon, especially one that deals one of the types of damage that hurt it, in which case it may teleport away to a safe distance or cast telekinesis to shove the attacker away. If a ranged attacker strikes it, or a spellcaster casts a spell worth dignifying with its attention, it casts telekinesis to yoink the impertinent whelp up to the front line. If an opponent within reach backs away, it uses Move to close the gap again. As mentioned before, it casts dispel magic to shut down sustained buffs and debuffs.
There may be a thing or two I’m missing here—I’ve been sick this weekend, and taking care of my daughter who’s also been sick, and I’m not firing on all cylinders. If you find something I missed, shout it out.
Next: ulitharids and mindwitnesses.