My own campaigns have never been very fiend-heavy, so I haven’t delved much into the ranks of devils, but as I’m looking at the merregon for the first time, I’m impressed by the idea that the souls of soldiers who served evil spend eternity fighting for the forces of hell without faces, only permanent iron masks. I can imagine Nazi footsoldiers being condemned to this fate, and I find the image satisfying.
Merregons are brutes, with exceptional Strength and Constitution; their Wisdom is above-average, but their Intelligence is ape-level. They’re immune to fire and poison; resistant to cold, to magic and to physical damage from nonmagical, non-silvered weapons; and mute. They can’t be frightened or poisoned. The only language they understand is Infernal. They have 60 feet of darkvision, which isn’t overwhelmed by the darkness spell, as darkvision usually is.
With their double Halberd Multiattack, merregons make effective, straightforward footsoldiers. But their effectiveness is increased dramatically when they fight in the presence of another fiend of challenge rating 6 or greater—for instance, a bone devil, erinys, pit fiend or amnizu. The two Halberd attacks in the merregons’ Multiattack become three, and if they’re adjacent to their superior, they soak up attacks meant for it.
Thus, the formation you’ll see most often is a line extending up to 60 feet to either side of an infernal commander, with a semicircle of merregons ringing the commander itself. These merregons act as the commander’s bodyguards, while those in the rest of the line gain an additional attack from being inspired by their commander’s presence. If they need to cover more ground, give the commander some lieutenants of an appropriate CR. If there aren’t enough merregons present to form a solid line, it’s OK to space them out at 15- to 25-foot intervals, because their halberds give them 10 feet of reach. If a merregon falls, its allies spread out to keep the line intact, if they can; if not, the line retracts toward the commander.
Merregons have no free will; even in the Nine Hells, they fight until they’re destroyed. They obey their commander’s instructions and stay in formation unless ordered to break it. They don’t choose their own targets; their commander chooses targets for them.
Narzugons are the spirits of evil paladins who’ve struck deals with devils and been pressed into leading legions of infernal troops. They ride nightmares, bound to their service by infernal tack, a magic item described in Mordenkainen’s Tome of Foes. Such nightmares “must respond to summons and commands from the wearer of the spurs,” according to the flavor text in Mordenkainen’s.
So does this mean the nightmares are always controlled mounts (“Mounted Combat,” Player’s Handbook, chapter 9), or does it mean they’re independent but always act in ways that benefit their riders? I’d say the latter, for two reasons. First, there are only three actions a controlled mount can take: Dodge, Dash and Disengage. This would preclude a nightmare from attacking with Hooves and from using Ethereal Stride to bear its rider onto and off of the field, which can be highly tactically advantageous. Second, intelligent mounts are always independent, and nightmares have Intelligence 10 and can understand two languages—all the evidence we need, as far as I’m concerned. Remember that independent mounts take their turns on a separate initiative count from their riders. Nightmares take direction from their riders, but they do it
on their own time no—on their riders’ initiative count! (Thanks to commenter Dan S for the catch.) This makes them effectively both controlled and independent—they have all the timing benefits of controlled mounts but can use their actions as independent mounts.
But back to narzugons. They also are brutes, with extraordinary Strength and exceptional Constitution. They also have extraordinary Charisma, but since they have neither spellcasting ability nor proficiency in any social skill, this is more proof against banishment than anything else. Their Intelligence and Wisdom are both high: they can plan, assess and target enemies’ weaknesses, and choose their battles with care. Being zealots, however, once they commit to a fight, they stay in it to the end, even on their home plane.
Narzugons have proficiency in Dexterity, Constitution and Charisma saving throws (yeah, you’re definitely not going to banish these guys)—but not Wisdom saves, although they do have Magic Resistance. Thus, even though spellcasters trying to manipulate them with Wisdom-save magic don’t pose much of a threat, they still pose a greater threat than other spellcasters do, so a spell such as hold monster, eyebite or Otto’s irresistible dance is going to draw their attention—and their wrath—to a degree that other spells don’t.
They have several offensive actions available to them, but only one of these is a weapon attack: Hellfire Lance. Lances, as a class of weapon, have a couple of special properties. Unlike polearms, with which they share the Reach property, they’re poor against targets inside that reach: attack rolls against a target only 5 feet away have disadvantage. Also, if the wielder isn’t mounted, they require two hands to wield. A narzugon isn’t going to drop its shield in order to fight with a lance if it has any other choice at all. Therefore, a narzugon never dismounts to fight, and if it’s unhorsed, its first priority is to get back on its steed.
If it can’t do that—say, if it’s grappled, or if the nightmare has been destroyed—the narzugon stops fighting itself and instead rallies its infernal minions, including the nightmare if it’s still around, to surround it and fight in its stead. It holds onto its Hellfire Lance as long as it can, but it no longer attacks with it. Only if its foes have destroyed its steed, broken its line of minions and engaged it in melee does it abandon its shield (reducing its Armor Class to 18) and use its lance two-handed to defend itself.
The narzugon’s Multiattack comprises three Hellfire Lance attacks and one use of either Infernal Command or Terrifying Command. Infernal Command is situational but short-term; Terrifying Command is all-purpose but, like a dragon’s Frightful Presence, good only the first time it’s used against any given foe.
Ideally, the narzugon uses its Terrifying Command at the earliest opportunity in which it can affect all its foes or a dozen of them, whichever is less, and won’t need to re-up it later. But if it does need to use it again to affect targets it missed the first time around, it does.
Infernal Command is sort of a fill-in-the-blanks ability, since so many devils are already immune to either the charmed or the frightened condition but so few are immune to both. It’s also somewhat unnecessary unless the narzugon’s foes have already demonstrated an ability to cast spells that impose those conditions. However, it costs nothing to use Infernal Command except the opportunity to use Terrifying Command instead, and if that’s already taken care of, the narzugon may as well use Infernal Command whether it knows it needs to or not.
As a commander of troops, the narzugon has to think about the big picture: What is the strategic goal of its side? Does it have a specific mission to carry out? Is it attacking or defending? What’s the makeup of its troops, what weakness(es) do they have, and who among the opposition is likely to be capable of targeting those weaknesses? Can it gain advantage from any feature of the terrain? Do its troops include a couple of capable myrmidons (barbed devils, erinyes, etc.) that it can bring along when its nightmare mount uses Ethereal Stride? Allow it to make use of as much intelligence as it may reasonably have gathered.
The narzugon’s first priority is to eliminate the greatest threat(s) to its own side, and its second priority is to strike the most painful blow at the other. If it’s attacking someone on the opposing front line, it times the nightmare’s movement and its own Hellfire Lance attack to occur together, meaning that
whichever goes first takes the Ready action, and whichever goes second gets to do a little bit more—a Hooves attack from the nightmare, a full Multiattack by the narzugon. This is unnecessary, because you can always time the nightmare’s turn to occur right before or right after the narzugon’s, whichever is of greater benefit. The nightmare charges in at its full flying speed, “galloping” through the air and making an attack with its Hooves, after which the narzugon strikes.
On the other hand, if the narzugon is attacking an enemy behind the front line, rather than use its movement, the nightmare takes the Ethereal Stride action to bear the narzugon (and, if applicable, its myrmidons) directly into its opponents’ midst. For extra-amazing effect, since narzugons aren’t often going to get to stage surprise attacks with all the troops they lead, on one turn you can have the nightmare fly-gallop forward toward its opponents, then use Ethereal Stride to vanish, and on the next turn you can have it reappear within the opponents’ ranks and deliver the narzugon to its objective.
The narzugon boldly sucks up hits from opponents who can’t hurt it significantly—those who are whacking or shooting at it ineffectually with mundane, non-silvered weapons—but anytime a foe manages to land a blow that actually hurts (deals 12 damage or more), it has its nightmare steed Ethereal Stride it away the next chance it gets. If the damage came from magic, the narzugon will reappear shortly thereafter behind the caster who hurt it and begin hurting them back.
Twelve damage is only a light wound for a narzugon, but it can’t take chances. It’s got only 112 hit points, which aren’t that many for a CR 13 creature, even one with so many resistances and immunities. Anyone who can hurt it at all is a threat to be eliminated. It does have Healing, a one-time action that lets it restore 100 hp to either itself or an ally, but there’s always the chance that the narzugon won’t receive that healing.
That being said, I have a hard time imagining an evil creature, even a lawful evil one, using such an ability to top up anyone or anything of lesser power and rank. The narzugon reserves Healing for itself, unless it’s on the field in the service of an archdevil that’s also present and taking major hits. Either way, the threshold for Healing is when the recipient is seriously wounded: in the narzugon’s case, when it’s reduced to 44 hp or fewer, and in the case of a superior devil, when it’s reduced to 40 percent of its hit point maximum. If the devil’s starting hit point maximum is 167 or greater, this will restore 100 hp; if it’s 166 or less, the devil will be fully healed back up. If both the narzugon and its superior are seriously wounded when its turn comes around, it heals its superior. That’s what makes it lawful evil.