When I picked the nightmare to look at in this post, I was thinking back to Advanced Dungeons & Dragons, in which it was simply the equine equivalent of the hell hound—an infernal horse, ridden by devils. Apparently, the lore has changed. Have you read the fifth-edition Monster Manual’s description of the nightmare? It’s not just some devil-horse anymore—now it’s what you get when you rip the wings off a pegasus. Seriously. That’s some sick stuff, man.
Give me a few minutes for the ick to wear off.
OK . . . whichever origin story you prefer, nightmares are clearly not evolved creatures, so they’re not going to possess the same survival instincts as most other monsters. They’re not undead, either, so there’s not necessarily any compulsion driving them. They’re categorized as fiends, so their primary motivation, underlying any other they may have, is malevolence. Their job is to transport devils and demons, and it suits them.
Aside from their average Intelligence, every one of a nightmare’s abilities is above average. Its physical abilities, especially its Strength, are exceptionally high, but it also has a curiously high Charisma. It doesn’t seem to use its Charisma for anything, so I think that’s simply a representation of their being difficult to banish (banishment is one of the tiny handful of spells that require a Charisma saving throw). You might think of it as a brute fighter, given that its highest two ability scores are in Strength and Constitution, but its speed also suggests a shock attacker element to its combat. It will try to maximize the damage it does on its first strike, but it won’t necessarily need to retreat after delivering that strike. Because nightmares’ flying speed is greater than their normal speed, they’ll move around the battlefield by flying leaps, unless something is preventing them from flying.
Nightmares are immune to fire damage, and they Confer Fire Resistance upon their riders. This would probably be more tactically valuable if they had some kind of Flame Aura feature of their own, but they don’t. So Confer Fire Resistance is more of an “oh, by the way” feature than a core capability. The same goes for Illumination, a primarily cosmetic feature with the side benefit of compensating for the nightmare’s lack of darkvision.
Ethereal Stride seems more interesting—at first. As an action, a nightmare can transport itself and up to three willing creatures into or out of the Ethereal Plane. What advantages does this offer? Chiefly, beings in the Ethereal Plane are invisible to beings in the material plane, making it a great way to get the drop on one’s enemies (unless they’ve got see invisibility or true seeing). Effectively having a surprise attack round at the outset of every combat encounter would be an outstanding trait for a shock attacker—except the nightmare has to use its action to emerge from the Ethereal Plane, giving it no chance to attack! Arrrrgh.
OK, but at least it can appear adjacent to an enemy, or appear within 90 feet and approach within reach of that enemy, so that if the enemy freaks out and tries to run, it gets an opportunity attack. Or—and I think this is the real utility of the feature—the nightmare appears adjacent to an enemy, and then its rider gets an immediate surprise attack. Moreover, the nightmare can carry its rider back into the Ethereal Plane after the rider’s next attack, through judicious use of the Ready action. (That is, if the rider takes its turn first, it Readies an Attack action to occur when the nightmare carries it onto the material plane; if the nightmare goes first, it Readies an Ethereal Stride action to occur immediately after its rider attacks.)
So basically what we have in the nightmare is a creature designed not as an attacker per se but as a delivery mechanism for other fiends, which just happens to have an attack of its own when it’s not busy carrying them into and out of the Ethereal Plane. Also, note that Ethereal Stride doesn’t just affect the nightmare’s rider—it affects up to three willing creatures within 5 feet of it. So you can have a “knight” fiend mounted on the nightmare, plus up to two “squire” fiends on foot alongside it. They just have to make sure they’re all grouped up when the nightmare blinks out again, so that they don’t get left behind.
Devils and demons typically don’t fear death on the material plane, because they can be truly killed only on their home planes, so a nightmare won’t need to flee on their account. I also can’t think of any reason why a nightmare should care enough about its own survival to flee when injured. After having its wings ripped off (sigh), it’s probably contemplating the misery of its existence 24/7 and satisfied to spend every last moment of its life taking its resentment out on someone else.
Here, then, is the basic pattern of nightmare combat:
- A nightmare appears in the midst of a group of enemies using Ethereal Stride, bearing a rider (usually a mid- to high-challenge devil, demon or yugoloth) and up to two other, lesser fiends. Those fiends then either execute Readied attacks, if their turns came before the nightmare’s, or attack on their own turns, if their turns come after.
- In intermediate rounds, the nightmare attacks on its own turn, and its allied fiends attack on theirs. A nightmare normally attacks whomever its rider is attacking; it’s not going to pick its own targets independently of its rider. But an unmounted nightmare will favor softer targets, i.e., those with a lower armor class. Or paladins, just because.
- At some point, the nightmare Readies an Ethereal Stride action, to occur when the last of its allied fiends has attacked—or, if it goes last in the initiative sequence, it simply uses this action. What’s the criterion for blinking out? It depends in large part on what the nightmare rider’s purpose is. Maybe the rider wants to get away from a group of enemies without incurring multiple opportunity attacks. Maybe it wants to launch a surprise attack on an isolated enemy who’s doing a lot of damage from a distance. Maybe it’s pursuing an equally mobile target. Or maybe its work here is simply done.