Mordenkainen’s Tome of Foes talks about “oinoloths,” e.g., “Oinoloths bring pestilence wherever they go.” But various (mostly older) sources, including the third-edition Manual of the Planes, refer to “the Oinoloth,” a singular individual, and even give the Oinoloth a name: Anthraxus, a highly apropos name for a lord of disease, though maybe not the most creative. (Also worth noting: The Oinoloth’s seat of power, the Wasting Tower of Khin-Oin, was situated originally in Hades, later in the Blood Rift, which begins in the Abyss and runs across the lower planes to the Nine Hells.)
Fifth-edition D&D seems to dispense with all that. The oinoloth’s listing in Mordenkainen’s refers to this fiend only in the plural and gives it a Challenge Rating of 12—exceeded by ultroloths’ CR 13. This hardly seems like the profile of an arch-ruler of yugoloths. Like the capital-M Minotaur, which D&D turned into a species of lowercase-m minotaurs, it appears that the capital-O Oinoloth has become a species of lowercase-o oinoloths—perhaps descendants of an earlier Oinoloth, although who’d want to produce offspring with an avatar of pestilence is a question probably best left unanswered.
The practical reason for considering this question is that if the oinoloth were a unique being, you’d only ever find one in any given combat encounter. But since fifth-edition oinoloths seem not to be unique, not only is it possible to run into multiple oinoloths at once, at very high levels of play it seems downright probable.
Even more than the yagnoloth, the oinoloth is a fiend without a weakness: its Strength and Charisma are extraordinary, and its lowest ability score is its very high Wisdom. It’s a brute by default, but it can play any position it needs or wants to. The thick of battle is a good place for it, however, because of its Bringer of Plagues trait, which creates a 30-foot-radius area of blight that poisons creatures within it if they fail a saving throw.
Or is it? If this trait is taken literally, other yugoloths—including the oinoloth itself, as well as any other oinoloth on the field—would do well to stay out of this radius: although they’re universally immune to the poisoned condition, they’re not immune to the necrotic damage that the trait deals on a failed save. This isn’t the first creature feature I’ve stumbled upon in Mordenkainen’s that I think may not have been fully thought through, and a clarification from the Powers That Be would be welcome. I’d be inclined to stipulate, at the very least, that oinoloths themselves are immune to this effect; other yugoloths, perhaps, as well. Alternatively (and, I think, preferably), the trait might be rephrased to indicate that only poisoned creatures take the necrotic damage.
Without one of these tweaks, the oinoloth could end up taking necrotic damage (which it’s neither immune nor even resistant to) from its own effect, and therefore it would be foolish not to hasten out of its blighted zone as soon as it created it. It also means it can’t plonk down a blight zone and sit tight in the middle of it, daring foes to come at it, because of the risk of randomly taking necrotic damage from time to time. If it’s not immune to its own plague, it has to keep moving around to stay out of its blight zones.
I’ll come back to this trait and to the oinoloth’s Innate Spellcasting in a moment, because how Bringer of Plagues works is key to figuring out its overall strategy. For the time being, let’s look at its actions. It basically has three to choose from on its turn: Multiattack (Transfixing Gaze plus Claw × 2), Corrupted Healing and Teleport. Unlike the nycaloth and the yagnoloth, the oinoloth has to use its entire action to Teleport. Corrupted Healing is a recharge ability, but it recharges only on a 6, so the oinoloth needs to wait for the right moment to use it, because there’s a good chance that it will get only one opportunity. Multiattack, therefore, is the go-to, with Corrupted Healing to be used only when the stars align.
The Claw attack alone is ferocious; two are savage. And that’s without Transfixing Gaze, which, if successful, charms and restrains the target, giving the oinoloth advantage if it chooses to Claw them. The effect lasts until the end of the oinoloth’s next turn, allowing it to Transfix a target, Claw at them with advantage twice, then, on its next turn, Claw at them with advantage twice more while attempting to Transfix someone else. And if that Transfixing Gaze succeeds, it can move on to the new target for a double-Claw-with-advantage on the following turn, and aim another Transfixing Gaze elsewhere . . . and so on.
Because of the power of chaining its Multiattacks like this, a good time to consider using Corrupted Healing is immediately after Transfixing Gaze has failed because the target succeeded on their saving throw. The side effects of Corrupted Healing—one level of exhaustion and a reduced hit point maximum—are of no consequence to a yugoloth ally, but if for some strange reason an oinoloth is fighting on the side of the player characters (either because it was paid to do so or because it was summoned with planar ally), just remember, oinoloths are neutral evil and couldn’t care less about informed consent. Their definition of “willing” is a “yes” to the question, “Do you want me to heal you and remove that debilitating condition?”
Since Corrupted Healing heals all damage and removes a debilitating condition as well, an oinoloth isn’t going to squander it on an ally that’s just suffered a few scratches. Also, yugoloths are all immune to the poisoned condition, and being deafened isn’t that big a deal compared with being blinded. So I’d say the minimum standard for Corrupted Healing is a target that’s either reduced to 40 percent or less of its hit point maximum, reduced to 70 percent or less of its hit point maximum and blinded, or reduced to 90 percent or less of its hit point maximum and paralyzed. And that goes for the oinoloth as well—it’s always willing and within 5 feet of itself. If it meets one of the first two of those criteria before any of its allies does, it uses Corrupted Healing on itself.
The oinoloth does, in fact, have a functional combo that includes Teleport, and that’s to combine it with Bringer of Plagues, which is a bonus action. Using its swifter-than-humanoid-average 40-foot movement speed, an oinoloth can swoop into the midst of a group of enemies, drop a plague zone, then Teleport out—or vice versa, Teleporting in and strolling back out, depending on whether the center of its desired blight zone is more or less than 40 feet from its current position. It’s not as satisfying as allowing the oinoloth to hold court in the center of its plague zone, but it definitely works.
Its at-will spells—darkness, detect magic, dispel magic and invisibility—work the same way for the oinoloth that they do for the yagnoloth, with the exception that an oinoloth won’t be involved in as many social situations and thus won’t have as many opportunities to scope out foes with detect magic. The real items of interest are its once-per-day spells: feeblemind, globe of invulnerability, wall of fire and wall of ice.
The oinoloth’s Intelligence isn’t quite high enough for it to be able to “read” enemies’ abilities at a glance, but it’s more than smart enough to judge, based on a round or two of observation, which of its foes are hommes sages and which are hommes singes. Wizards (Intelligence too high) and melee meatwads (can’t cast spells) are both poor targets for feeblemind; the ideal candidate is a bard, cleric, sorcerer or warlock with merely average brainpower, although a paladin or ranger will do in a pinch. Aside from low-to-average Intelligence, the key deciding factor in target selection is that the target is actually causing the oinoloth significant pain or inconvenience.
Globe of invulnerability is useful and powerful enough that the oinoloth may seriously consider casting it right away, as its first action. To affect it with a spell of 5th level or lower, an enemy spellcaster will have to come inside the globe, meaning within 10 feet of the oinoloth. There’s no downside to that, aside from the fact that concentrating on globe means not concentrating on darkness or invisibility. No squish wants to get that close to an oinoloth. There are too many insensitive things it can do to them, from Transfixing Gaze to Claw attacks to Bringer of Plagues to wall of fire.
There’s a trick I’m particularly fond of in which a monster that’s immune to fire damage, such as an efreet, casts wall of fire in a ring around itself with the flames pointing inward, grilling every enemy within 10 feet of it. This trick works less well for the oinoloth, which is merely resistant to fire damage, not immune; it can reasonably expect to take just 8 damage per turn it’s in the flames, but that’s still 8 damage it doesn’t need to take, even if its opponents are taking twice that. A more likely play for the oinoloth is to take advantage of terrain and obstacles and cast wall of fire and/or wall of ice to trap enemies inside a blight field. Wall of ice obstructs movement completely until characters bash through it; wall of fire simply forces an unpleasant choice between fire damage and necrotic damage. This trap is easier to set up if the oinoloth doesn’t take necrotic damage from its own blight field, because it can use Bringer of Plagues and cast a wall spell in the same turn without having to exit the field (obviously, if the oinoloth’s enemies would take damage from wall of fire on the way out, so will the oinoloth) or take necrotic damage.
OK, so . . . having established all that, when and how does an oinoloth use Bringer of Plagues, which is clearly meant to be its centerpiece trait? “When” is whenever it can: A 5–6 recharge indicates a feature powerful enough to be superior to most if not all other options, whose use therefore needs to be limited. “How” is the trickier question to answer, because as I’ve belabored, it depends on whether or not the oinoloth and allied yugoloths can take necrotic damage from it.
But it also depends—possibly even more—on why the oinoloth is there to begin with. What’s the military objective? Is it just looking to kill, or is it defending a position? In the latter case, it’s not necessarily going to be concerned with how many enemies are in the radius of Bringer of Plagues when it uses that trait. Instead, it’s going to use it to turn the approach to whatever it wants to keep others out of into a gantlet of toxic damage fields, with cleverly placed wall of fire and wall of ice to make progress through those fields tortuous and time-consuming. On the other hand, if its ultimate goal is merely to sicken as many opponents as it can, it’s going to treat Bringer of Plagues as an area-effect spell with a 30-foot radius and therefore get in position first to affect at least six enemies—or all of them, whichever is less.
How about target selection? Again, depends in large part on its mission, and on which of its foes is most likely to effectively interfere with it. Oinoloths have Magic Resistance and proficiency in Constitution and Wisdom saving throws and are immune or resistant to the types of damage most commonly deployed via evocation spells, so they’re not particularly threatened by spellcasters. They’re resistant to physical damage from normal weapons—meaning anyone wielding a magic weapon against them is a person of interest. Less tough-looking opponents probably have lower Constitution save mods, making them easy pickings for Bringer of Plagues; Transfixing Gaze is most effective against those foes who look like they’ve opted to emphasize the physical over the mental. There’s no simple, hard-and-fast rule—because oinoloths have no real weakness to target, and thus no particular enemy who screams to be taken out first. They simply adapt to the situation, whatever it is.
Like other yugoloths, oinoloths are happy to go to the mat on any plane except the one they were born on. If they’re seriously wounded (reduced to 50 hp or fewer), they bargain for their lives—dishonestly, of course, since they’re proficient in Deception, not in Persuasion.
Next: duergar from Mordenkainen’s.