Duergar Tactics: Mordenkainen’s Duergar, Part 1

The central question in running duergar—which otherwise are simple and straightforward brute fighters—is when to use Enlarge and when to use Invisibility, the complication being that Enlarge both breaks invisibility and takes an action to execute, preventing a duergar from attacking on the same turn. Thus, any additional damage it deals from being Enlarged has to make up for the round in which it deals no damage at all. As I note in an earlier post, the break-even point for ordinary duergar is in the third round of combat. Over just one or two rounds, Enlarging doesn’t add enough damage to make up for the lost round. Over four or more, it offers a clear advantage. Thus, the more likely a fight is to drag out—in other words, the more evenly matched the two sides—the greater the benefit of Enlarge. Invisibility, meanwhile, is really useful only for either ambush or flight, since it’s a once-per-combat feature that’s disrupted by attacking, casting a spell or Enlarging.

Interestingly, not all the duergar in Mordenkainen’s Tome of Foes possess Enlarge and Invisibility. In fact, only four of the seven duergar variants in Mordenkainen’s have these two features, and one of them has Invisibility on a 4–6 recharge, resulting in a big increase in the breadth of its usefulness. Also, while most of the variant duergar are also brutes, one is a quasi-spellcaster (it has no spells to cast, but it does have an Intelligence-based long-distance offensive ability), and one is a shock trooper. Finally, alongside those seven variants, there are two profiles of constructs that duergar employ. As I go through the various stat blocks, I’m going to focus primarily on how these variants differ from run-of-the-mill duergar.

Duergar soulblades are the shock troops, relying on their high Dexterity for both offense and defense. Their primary weapon is their (surprise!) Soulblade, a psionic melee weapon that deals bonus damage when the duergar attacks with advantage. For this reason, gaining advantage on attack rolls is central to the duergar soulblade’s strategy, and it happens to have a couple of different ways of doing this built-in. One is its Invisibility; the other is true strike, a mostly useless cantrip whose one practical application is to gain advantage on the first attack roll in a combat encounter. (Gaining advantage is useful; the problem with true strike is that it consumes a full action to cast, so the caster gives up one whole attack action in order to gain advantage on another. This tradeoff is never worth it unless you weren’t going to use that first action to attack anyway.)

Duergar soulblades can cast true strike at will, but seriously, what’s the point? There’s no good time to cast it except right before the start of a combat encounter. Which means that duergar soulblades don’t necessarily want to start combat already invisible. That would be redundant: gaining advantage from more than one source doesn’t grant you more advantage.

In other words, while duergar soulblades have two built-in sources of attack advantage, they get only one use of each per encounter, and each of them takes an action—and therefore a full turn—to set up. This fact sends my mind in the direction of thinking, what if duergar soulblades plan to spend only two combat rounds attacking, period? What if, in fact, they’re only employed when a unit of duergar know that a fight is going to happen and that it’s going to be prolonged, and want an underhanded way to swing the battle dramatically in their favor?

I’m getting a little ahead of myself in sharing this conclusion, because I haven’t talked about two of the duergar soulblade’s other “spells” (really psionic abilities), jump and hunter’s mark. Let me just say, bringing these two powers into the mix is going to make things crazy.

I suspect that both players and DMs alike underuse jump because the rules governing jumping are so complicated compared with the rest of fifth-edition Dungeons & Dragons, so I’ll do all the heavy lifting for you right now. Jump triples a creature’s jumping distance—but it does nothing to the creature’s speed, so what you often end up with is a creature that can jump farther than it can move in a turn, and by extension, a creature that begins a jump on one turn and completes it on the next. The duergar soulblade, like most dwarves, moves only 25 feet per turn. Its running long jump distance is 11 feet, its standing long jump distance 5 feet, its running high jump distance 3 feet, and its standing high jump distance 1 foot. Jump increases these distances to 33 feet, 16 feet, 9 feet and 4 feet. It takes an action to cast and lasts 1 minute without concentration.

So here’s a hypothetical duergar soulblade attack sequence, which begins at the same moment its other duergar allies initiate combat:

Round 1. The duergar soulblade, hiding out 40 feet away from where the action is going to occur, casts jump on itself.

Round 2. The duergar soulblade gets a 10-foot running start, then leaps 30 feet toward its enemies. However, it’s only able to complete 15 feet of its jump, so it ends its turn still 15 feet away from its foes. While in midair, it casts true strike as an action and uses Create Soulblade as a bonus action. (It could have used Create Soulblade in round 1 instead, but this way is more cinematic, don’t you think?)

Round 3. Still in midair, the duergar soulblade casts hunter’s mark as a bonus action Doesn’t work—see Josh C’s comment and my reply below. Then it completes its movement, lands next to an opponent and uses its action to attack with its Soulblade. It gains advantage from true strike, and having advantage also gives it an extra 1d6 force damage on a hit. Throw in yet another 1d6 from hunter’s mark, and the duergar soulblade is dishing out 3d6 + 3 force damage. (Unless it’s also Enlarged—then it’s dishing out 4d6 + 3 damage! But unless all its duergar allies have pre-Enlarged themselves as well, I wouldn’t assume that the soulblade has time to do so.)

Round 4. The duergar soulblade casts hunter’s mark again, then uses Invisibility to vanish from view. (It has to do it in this specific sequence, because casting a spell breaks its invisibility, and losing invisibility means losing advantage.)

Round 5. The invisible duergar soulblade attacks again, with unseen-attacker advantage, gaining both its “advantage damage” and the extra damage from hunter’s mark if it hits. Ideally, this finishes the fight. This whole sequence doesn’t work either—see Jacob L and JP’s comments below. Invisibility and hunter’s mark are either-or. And the choice is a no-brainer: hunter’s mark confers an extra 1d6, but Invisibility confers advantage and an extra 1d6.

It’s elegant and awesome-looking, albeit slow. But let’s be hard-nosed and compare the damage it deals to the lesser elegance of a straight fight. In the sequence above, the duergar soulblade gets only two attacks, both with advantage, dealing 3d6 2d6 + 3 damage on each hit the first hit and 3d6 2d6 + 3 on the second. Against, say, AC 15, we’re looking at 22 19 16 total expected damage (27 24 20 average damage over two hits, 80 percent chance to hit). In contrast, what if it just stood there and dully swung its Soulblade for five rounds, neither seeking nor obtaining any source of attack roll advantage? Here the math is a bit trickier because the 55 percent hit probability is low enough that we can’t know for sure how much of an impact hunter’s mark will have—it’s entirely possible that the duergar soulblade will lose one or more uses of it owing to its concentration being disrupted after a missed attack. Let’s suppose that out of five attacks, the duergar soulblade gets to apply hunter’s mark damage on two hits but loses its third use to broken concentration. All told, we’re looking at 18 expected damage over five attacks, plus another 7 from hunter’s mark, for a total of 25. That’s slightly significantly better than the jump­-powered, slow-motion banzai charge I came up with above.

But wait—shock troops aren’t just going to stand in one place swinging a sword for five rounds. That’s brute style. It’s not how they work. For one thing, they don’t have the staying power: duergar soulblades have only 18 hp, vs. the standard duergar’s 26 hp. Their Constitution is merely average, their Armor Class only 14. Shock troops get in, wreck face and get out. The “get out” part matters. And what mechanism does the duergar soulblade have for getting out of a fight? None, other than killing its opponent! Jump, alas, does not have a Disengage action built into its effects, and the duergar soulblade is already using Invisibility to gain advantage on a second attack roll; it’s not available for evacuation.

In any reasonably close matchup, a player character can probably take out a visible, stationary duergar soulblade in a head-to-head fight in three rounds (if the soulblade doesn’t take them out first). It’s not going to have five rounds of attacks; it’s only going to have three, and two of those at most will have hunter’s mark damage attached. So the real expected damage total we should be looking at is 11 over three attacks, plus the 7 from hunter’s mark, or 18 damage. With this, the jump assault compares favorably still falls short but at least is in the same ballpark. Plus, no one else attacks quite that way. So let’s stick with it.

Of course, having said that, now I’m going to bring up an exception. In total darkness, against creatures without darkvision, duergar don’t need Invisibility or true strike to gain advantage on their attacks; they have it by default. Thus, those intermediate steps aren’t necessary—even jump isn’t necessary, really, because they don’t have to start at a distance to avoid engagement long enough to cast true strike. They can join the fight immediately, alongside their comrades, and julienne away. But that’s only if none of their foes has darkvision. Duergar aren’t walking encyclopedias, but they know which other humanoid species have darkvision and which don’t.

Duergar soulblades have the common sense to retreat when seriously injured (reduced to 7 hp or fewer), but they’re fairly indiscriminate in their target selection.

Duergar stone guard are essentially normal duergar, but tougher and better-armored, with the Phalanx Formation trait. Phalanx Formation works similarly to Pack Tactics, granting advantage on attack rolls while adjacent to “a duergar ally wielding a shield” (i.e., another stone guard, a duergar warlord or a regular duergar—duergar kavalrachni carry shields as well, but they’re mobile); it also grants advantage on Dexterity saving throws. The stone guard need this advantage, because their King’s Knives do less damage than the regular duergar’s war pick.

Duergar stone guard make their Enlarge and Invisibility decisions the same way standard duergar do. The only difference in their fighting style is their deployment, which is used either to block for a line of javeliniers or xarrorn behind them or to keep foes out of a strategically important location. When half or more of a line of stone guard are seriously wounded (reduced to 15 hp or fewer), they Disengage and fall back in formation, always keeping the shield wall intact.

Duergar xarrorn are brutes that will engage enemies in direct melee if they don’t have duergar stone guard to block for them. They have two offensive actions: Fire Lance, a standard melee weapon attack with a long reach, and Fire Spray, an area effect with a standard 5–6 recharge that’s always used against at least two foes, never just one. If the xarrorn needs to reposition in order to strike two or more, it does so.

The recharge suggests that Fire Spray is the preferred action whenever it’s available, and as long as a xarrorn isn’t Enlarged, it is. But an Enlarged xarrorn can do more damage with its Fire Lance as long as it has at least an 81 percent chance to hit. That means having advantage against a target with AC 14 or lower. (The xarrorn isn’t smart enough to read a PC’s Armor Class off their character sheet, so it would rephrase that as “a target wearing light armor or none, or hide armor or a chain shirt without a shield.”) If those two criteria are met, it always favors the Fire Lance.

Xarrorn use the same criteria for Enlarge as regular duergar do, and they also turn invisible and flee when seriously wounded (reduced to 10 hp or fewer).

The duergar kavalrachni are, as you might guess from the name, giant spider cavalry (araignery?). They ride steeders (also in Mordenkainen’s), specifically female steeders. Their Cavalry Training trait lets a kavalrachni follow up a successful attack with an attack roll by its steeder mount, which is good by itself and even better if you treat the steeder as an independent mount rather than a controlled mount (although, based on their flavor text description and their paucity of features, you may not want to—I probably wouldn’t).

Kavalrachni can attack at range, but their ability contour is such—and their Multiattack good enough—that they’re quite happy to charge into melee. Their Heavy Crossbow attack is useful for making ranged attacks while they’re on their way to a melee engagement and for taking potshots as they depart. Because the typical function of cavalry is to smash through a front line and run down more valuable targets behind it, this is what kavalrachni do, even though they have no particular acuity for choosing one target over another; the fact that an enemy is sheltering behind the front line is evidence enough that they should be run down.

One of the subtleties of fifth-edition mounted combat is that if a controlled mount provokes an opportunity attack, the attack may target either the mount or the rider—but if the mount takes the Disengage action, it exempts both the mount and the rider from opportunity attacks, since the rider is moved out of its opponent’s reach by its mount’s movement, not by its own. Thus, when a kavalrachni doesn’t need its mount to Dash in order to reach its opponent, but it does need to pass through one or more opponents’ zone(s) of control, the mount Disengages. (If it doesn’t need to pass through any opponent’s zone of control, the mount Dodges.)

Shared Invisibility gives the kavalrachni ambush potential; regular duergar usually use their Invisibility to retreat rather than to attack, but a quirk of the Shared Invisibility feature, combined with steeders’ mobility, makes invisibility less necessary for a fleeing kavalrachni. This quirk is that Shared Invisibility allows a steeder mount to make an attack without disrupting the invisibility of the duergar riding it. (In contrast, if the duergar kavalrachni attacks, both the steeder and the rider become visible.) This allows a rider-mount pair to approach invisibly, the steeder mount to attack with advantage, then the kavalrachni to make its first attack with advantage as well. However, this sequence only works if the steeder mount is independent rather than controlled: a controlled mount can only Dodge, Dash or Disengage. Allowing the steeder mount to act independently also allows a kavalrachni-steeder pair to perform a more effective leaping assault than the duergar soulblade can manage, because the wording of the steeder’s Extraordinary Leap differs from the wording of jump: “every foot of its walking speed that it spends on the jump allows it to move 3 feet,” meaning that it doesn’t have to spend two turns’ movement to cover the extra distance.

Kavalrachni have a double War Pick Multiattack, no doubt to make up for their inability to Enlarge. This makes them stronger than regular duergar, but not significantly so. If they’ve used their Shared Invisibility to attack, they need something to enhance their retreat, such as a mount that can Disengage on their behalf. Thus, a kavalrachni retreats not only when it’s seriously injured (reduced to 10 hp or fewer) but also when its steeder mount is seriously injured (reduced to 12 hp or fewer). The steeder’s Disengage action is the kavalrachni’s ticket out of a losing fight; it’s not going to squander it. However, an independent steeder mount, being a predator that doesn’t like it when prey fights back, is liable to nope out prematurely, when it’s only moderately wounded (reduced to 21 hp or fewer). Controlled steeder mounts stay in the fight as long as their riders need them to.

Next: the duergar mind master, warlord, despot and constructs.

22 thoughts on “Duergar Tactics: Mordenkainen’s Duergar, Part 1”

  1. Would it be fair to say that Soul Blades would best used in an encounter with other types of Duergar? For example the Stone Guard would hold the front line against PCs whilst Soul Blades use their invisibility to get into position to attack the PCs back line, they then use the jump based attack sequence described above (which is too cool not to use in my opinion) to attack and ranged/spell-slingers the PCs might have?

  2. Am I mistaken, or in your 5 step Soulblade attack plan, would true strike drop when the Soulblade casts hunter’s mark in turn 3? Both spells are concentration, so would that mean choosing between the effects of Hunter’s Mark or True Strike on the third turn before they make their first attack of the combat?

    1. Mmmm, you’re right. True strike and hunter’s mark are either-or. So which one’s better? No contest—true strike! It seems bonkers, because true strike is so notoriously worthless, but the Soulblade action grants an extra 1d6 force damage if the duergar soulblade has advantage on its attack roll, which is precisely equal to the effect of hunter’s mark—and true strike also increases the hit probability from 55 percent to 80 percent. Let’s say, then, that the soulblade resorts to hunter’s mark on any attack roll it can’t gain advantage on, so that it can still at least get that extra 1d6 damage.

  3. Looking at the Soulblade’s epic jump tactic, I sadly see a flaw involving concentration. True Strike, Hunter’s Mark, and the Soulblade’s Invisibility feature require concentration, so casting one will break concentration on another. Unless I missed something, the sequence would have to lose Hunter’s Mark altogether for the Soulblade to maintain its advantage on attacks in this scenario.

    1. True in the case of true strike and hunter’s mark, but Invisibility gets by on a technicality: Per PH 203, “You lose concentration on a spell if you cast another spell that requires concentration” (emphasis mine). Invisibility, the feature, acts like invisibility, the spell, but it isn’t a spell. It’s just a feature that consumes an action. In the other direction, however, the wording of Invisibility explicitly states that casting a spell breaks it.

      1. Wouldn’t the phrasing “…(as if concentrating on a spell)…” under the Invisibility feature cause it to be treated as though it were cast as a spell?
        …or is that phrase merely meant to show that the ability may be interrupted by damage and benefit from abilities like the “War Caster” feat as actual concentration spells would be?

          1. No, it requires concentration, and you cannot concentrate on two things at a time, whether or not both are spells. There are non-spell player abilities that require concentration as well. A Trickery cleric must concentrate on their Channel Divinity option to get an illusory double, which will vanish if they cast a concentration spell (and vice versa, if the concentration spell is cast first). The Duergar Invisibility feature is no different, though they can be Enlarged and Invisible if they Enlarge first. This involves sacrificing two whole rounds though, so it’s not likely to be worth it unless the duergar have successfully concocted an ambush.

          2. Can you cite a ruling on this? I looked for one and found nothing. In the absence of a clarification, absolutely literal interpretation is the way to go in 5E.

  4. Bonus points for using the soulblade tactic off a high point.. imagine thinking an encounter will be easy, the having 3-5 soulblades fall on your head.

    1. No, that’s not how it works. You can begin a jump no matter how much movement you have, but if the jump distance exceeds your speed, you won’t be able to finish it in the same turn unless you Dash, and maybe not even then (if under a jump spell). You can certainly end a turn in midair—flying creatures do it all the time. However, if someone knocks you prone in the middle of that long-distance jump, and you don’t have the ability to hover, you’re going to fall down to the ground.

  5. Invisibility and Hunter’s Mark are also both concentration. The Soulblade runs into the same logjam as with true strike.

  6. The Invisibility feature states that Enlarge would break invisibility but what if the duergar Enlarged first (which does not require concentration) and then used Invisibility on its next turn?

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