I’m puzzled as to why certain creatures are included in the “Miscellaneous” Appendix A of the fifth-edition Monster Manual, which consists mostly—but not entirely—of regular animals, such as apes, bears, crocodiles and so forth. Why, alongside this menagerie of mundane beasts and their oversize cousins, do we also find awakened trees and shrubs, blink dogs, death dogs, wargs (excuse me, “worgs”) and phase spiders? Why didn’t these monsters (none of them is categorized as a “beast”) rate their own listings in the body of the book? So odd.

Phase spiders differ from giant spiders in a variety of minor respects and two significant ones. First, while they have the Web Walker feature, they don’t spin webs. This struck me as so peculiar that I checked the MM errata to confirm that it wasn’t a mistake. Second, they have the Ethereal Jaunt feature, which lets them phase back and forth between the material plane and the ethereal plane.

I’m going to take a quick look at its other traits and then come back to these, because I think the phase spider is in need of some flavor text that explains what it’s all about.

Phase spiders are brute fighters, with high Strength and Dexterity and above-average Constitution. With Intelligence of 6, they’re also cleverer than you’d expect a spider to be. Although they’re not clever enough to act beyond their instincts, those instincts can take them a long way: Intelligence 6 is equivalent to that of a chimp. It’s not unthinkable that a phase spider might even use tools. Finally, the combination of Stealth proficiency and darkvision makes phase spiders nighttime or underground ambush predators.

So we have an ambush predator that can navigate webs but doesn’t create them. Why the former ability and not the latter? And why the ability to phase back and forth between planes? Here’s my theory: Phase spiders didn’t evolve independently. Rather, they’re the result of a magical hiccup in the evolutionary process. Something created them out of regular giant spiders, and they continue to live side by side with their mundane sisters. In fact, that lovely cornflower blue illustration notwithstanding, I imagine that a phase spider is indistinguishable from other giant spiders until it begins blinking.

But wait a second. Spiders, by and large, are solitary creatures. In our world, there are tens of thousands of known spider species, yet fewer than two dozen of these are social. On the other hand, as a practical matter of gameplay, giant spiders cease to be boss monsters when our player characters hit level 2. We send groups of giant spiders at our players all the time. You’ve done it. I’ve done it. So I guess we have to say that in Dungeons and Dragons, giant spiders just happen to be one of those social species, or at least subsocial. And phase spiders, occasionally, live among them.

Fighting on their own, giant spiders will first seek to ensnare their prey in a web, if the prey isn’t caught already. Then, once the prey is restrained, they bite (with advantage) to paralyze. When the prey stops moving, they wrap up their treat to enjoy the leftovers later.

Phase spiders act in conjunction with this behavior, but since they don’t make webs of their own, they aid their sister spiders by taking out moving targets, gaining advantage as an unseen attacker by using Ethereal Jaunt to appear suddenly behind their prey. Phase spider poison is no stronger than regular giant spider poison (we can infer this from the DC of the saving throw, which is the same), but the phase spider delivers a lot more of it (we can infer this from the greater damage it does, 4d8 vs. 2d8). Thus, contrary to predators’ usual habit of primarily targeting the old, the young, the weak, the isolated and the oblivious, a phase spider may attack the larger of its opponents, knowing on some dim level that it has a better chance of taking them out than other giant spiders do. Plus, as a brute fighter, it’s more inclined toward aggressive melee engagement.

Phase spiders follow different action patterns based on whether they’re “blinking in” (ethereal to material) or “blinking out” (material to ethereal). When blinking in to ambush, a phase spider first uses its Ethereal Jaunt bonus action, then its Bite action. (To be fair to your PCs, the phase spider should make a Dexterity (Stealth) check, opposed by its target’s passive Perception, to determine whether it can appear behind the target without being noticed. If it fails, it loses its advantage on the attack.) When blinking out to escape a foe who’s hurting it, it delivers a Bite out of spite, then uses the Ethereal Jaunt bonus action to vanish.

What if a phase spider blinking in to attack successfully paralyzes its prey on its first strike? Then it uses its movement to bring itself closer—within melee reach, if possible—to another opponent who does fit the usual prey profile. Bigger opponents are for engaging only with stealth strikes.

Once it’s engaged with a target, a phase spider remains engaged with that target until the target is paralyzed or the spider takes moderate damage (10 points or more in a single round). If a phase spider takes that much damage in a round, it bites once more, then blinks out. When a phase spider is seriously injured (reduced to 12 hp or fewer), it blinks out and doesn’t return.

Next: shoosuvas.

This article has 13 comments

  1. Florian Albrecht Reply

    So basically like a fancier, brawlier Giant Wolf Spider, with ethereal jaunt and more HP instead of the stealth bonus?
    I like the idea of Giant spiders (at least the non-webbing kind) as somewhat social insects. In terms of ecology, I am imagining a nest or colony, somewhere in the underdark or somewhere, with specialized casts having evolved to do different kind of tasks, like some kind of creepy beehive or anthill. Or at least some type of mutualism of various spider-families, with Wolf Spiders alerting the others of incoming prey and Phase Spiders herding them into Webs made by the normal Giant Spiders.

  2. Matthew Vienneau Reply

    I like your idea of Stealth vs. Passive Perception when blinking in.

    At first I thought you meant in the first round, when surprise is being determined. I then imagined the phase spider surprising the PCs every round, which isn’t possible.

    So it sounds like you’re talking about later rounds and using the Unseen Attacker rule where you get advantage if you can’t be seen, and you’re saying the PCs should get a chance to see it because they’re expecting it to appear somewhere?

    I’m also expecting the PCs will have attacks “readied”, and I’m not sure how to rule on them. The spiders are going to try and appear behind/above the PCs, who will likely be whirling around, maybe standing back to back. It seems unfair to not let them attack when the spider appears, though to always get first attack seems to take away the point of being able to phase in and out in the first place (unless the spiders phase in order and all attack the same person? Seems cruel!).

    I’m looking forward to the tactical challenges of the battle (it’s tomorrow night) and I want to make sure I know all my rulings ahead of time to keep the pace flowing.

    • Keith Ammann Reply

      Compare the phase spider to a creature that’s actually invisible. The invisible creature attacks while it still can’t be seen, then immediately appears. So that’s a clear-cut case of unseen attacker advantage. But when a creature comes out of hiding and then attacks, there’s that brief moment when it might be spotted, and so it has to make a Stealth check to make sure it’s still unseen when it does attack. That’s why the phase spider needs to make a Stealth check between when it phases in and when it attacks.

      A PC who Readies an Attack action to occur when a spider appears within reach has to know that the spider has appeared. So if the PC’s Perception beats the spider’s Stealth, the PC’s Readied Attack comes first, then the spider’s attack. If the spider’s Stealth beats the PC’s Perception, then the spider gets to attack first, after which the PC takes his or her Readied action. It all comes down to when the PC realizes the spider is there: when he or she hears its legs skittering across the stone, or when he or she feels its fangs sink in.

  3. SETH R FELDMAN Reply

    Rules As Written, that’s not how them appearing as a bonus action would work. There’s no facing in the combat rules for 5e, just a space you occupy. There’s no
    hybackside like that to appear behind. Appearing would reveal them, as it is a bonus action to change planes. That’s done and they’re visible to a player controlling their space, as they move to take the Bite action.

    Following from that, the shift in to attack doesn’t really help them strategically, aside from positioning – that said, a round later, when they can use it to phase out after attacking, it makes them very hard to harm.

    • Keith Ammann Reply

      That’s one interpretation of the RAW. Here’s mine: People don’t have panoramic vision. If you have darkvision, you can see in the dark. If you have truesight, you can see through illusions and into the ethereal plane. If you have blindsight or tremorsense, you draw on senses other than sight to detect creatures around you. Only blindsight and tremorsense, which have radius without direction, would allow you to perceive a creature in a direction you’re not looking in.

      Jeremy Crawford calls D&D “a game of exceptions,” in which a general rule always applies unless it’s overridden by a specific rule. I take this one step further: Reality always applies unless it’s overridden by a D&D rule. Thus, only an in-game fact (e.g., dragons exist, wizards can cast spells that let them float in the air) can supersede a real-world fact; the absence of a rule cannot. RAW, although there are tables for lifestyle expenses and food and drink, there’s no consequence for refusing to pay and deliberately starving. A DM has to draw the line between the fanciful and the outright absurd.

      Sounds like you’ve had some bad run-ins with rules-lawyering players.

  4. Toothbrush Reply

    Very interesting article!
    My two cents : Phase spiders could be predators of giant spiders, taking a giant spider’s lair (since it cannot spin its own web), with its food, leaving it when it has gone too old (can’t repair it!).
    Or, with a more “social” view of these nasty spiders (like Florian Albrecht said), they could be their rulers, or their more warrior-type individuals.
    A very old phase spider, swollen by years of feeding on nasty spidery fluids, lurking in its (borrowed) deep lair. Ah. LOTR.

  5. Rogue Scientist Reply

    I see web walk as implying they still have spinerets, they just don’t have the ability to ‘fling’ webs like some other spiders. They may still spin webs. Imagine no signs on the material plain, but their ethereal demesne entirely surrounded with ghostly webs, ceiling covered with web sacks of nothing but dry bones (the only remains of previous victims)…

  6. McDunno Reply

    A phase spider’s teleportation does not grant it advantage in combat. An ability that grants advantage has to specifically state that it does, such as a Monk’s shadow step.

    • Keith Ammann Reply

      Phase spiders don’t actually teleport—they move back and forth between the material and ethereal planes. And it’s not Ethereal Jaunt itself that confers advantage, but rather the act of attacking while unseen, which is specifically stated to confer advantage. As long as the phase spider attacks before its prey sees it, it has advantage. This is why I recommend the additional Stealth check, to give the target a chance of seeing it before it strikes.

  7. McDunno Reply

    I was using teleport as a shorthand term, not as a game mechanic. There is nothing in the description that states a phase spider gains the hidden condition, either. I can see using the phasing to gain surprise on the first round, but a creature cannot hide in combat unless they use an action to do so. If phasing were intended to impart the hidden condition to gain advantage, it would state that explicitly, just as shadow step explicitly states the teleporting monk gains advantage but the misty step spell does not.

    • Keith Ammann Reply

      A creature can become unseen in combat by doing anything that makes it unseen. It doesn’t have to be a Hide action. It can be an invisibility spell. It can be a darkness spell. It can be something like Shadow Step. Or it can be something that brings it into the material plane from another plane in an out-of-view location.

  8. McDunno Reply

    Those are completely different effects. A creature that is invisible can attack while invisible. It becomes visible after it attacks. A creature in the ethereal plane must appear in the prime material plane before it attacks. It cannot attack before it appears. If you want to rule that phasing has the potential to grant the hidden condition at your table, I have no argument there. But it’s not RAW, and you shouldn’t present it as if it were.

    • Keith Ammann Reply

      Yes, it must appear in the prime material plane before it attacks. And it can still appear out of somebody’s field of view, and if it does so, it’s unseen unless and until it gives itself away (e.g., by attacking, or by failing a Stealth check).

      This is RAW: “When a creature can’t see you, you have advantage on attack rolls against it” (PH 195). In this case, ”you” is the phase spider. There is no condition called “hidden.”

      You can be as argumentative about this as you like, but I’m standing my ground on this one.

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