If spiders give you the heebie-jeebies, you'll want to brace yourself for the acid-spitting, magic-resisting, spell-casting demons known as spyder-fiends. Waiting for your party in Vecna: Eve of Ruin, these abyssal entities are infamous for their cunning tactics, ruthless depredation, and the fact that they are spiders with freaking wolf heads. Even worse, they're intelligent enough to talk, and some even have humanoid arms that can hold weapons.
If that description alone isn't enough to nope you out of the article, come along for a look at these creepy crawling carnivores you're likely to encounter during the events of Vecna: Eve of Ruin:
What in the Abyss Are Spyder-Fiends?

Hailing from the Abyss, demons are chaotic evil incarnate. Their sole purpose is to wreak havoc across the multiverse, and that's kind of what they base their whole personality and vibe on—even their names are hard to pronounce.
Seeing as spyder-fiends are demons that follow (and might have been spawned from) the demon lord Miska the Wolf-Spider, they embody a nightmarish spider-wolf fusion and are as dangerous as you'd expect from this rather horrifying hybrid of apex predators.
Miska's Minions
Miska is a demon lord who's been stuck behind bars in a demiplanar prison on Pandesmos, the first layer of Pandemonium, ever since he tried to take over the multiverse alongside the Queen of Chaos a couple eons ago. Despite their chaotic nature, Miska's spyder-fiends are unwaveringly loyal servants to the incarcerated Prince of Demons and continue to scheme and work toward getting their master paroled.
Tactical Killing Machines
Spyder-fiends' favorite pastime is brutally killing their foes, which they're unsurprisingly good at. However, they aren't mindless killing machines. You wouldn't necessarily expect a gore-splattered Fiend with a wolf's head and spider's body to be capable of keen calculation. But, in spite of their appearances, spyder-fiends can be deceptively strategic in battle.
This knack for tactics can most likely be attributed to their connection to Miska, one of the most prominent and successful demon lord generals. Back in his heyday, Miska was a formidable lieutenant in Chaos's army, almost pushing the forces of Law to defeat.
Since Miska's imprisonment, spyder-fiends have been left to their own devices, but when they fight, they do so in organized ranks and make ingenious use of their webs to disadvantage their targets.
Jealous and Ambitious
Spyder-fiends are a cutthroat bunch. They choose their leaders based on strength and cunning, and constantly vie to increase their status.
As they grow in power and intelligence, they scheme against their superiors and will happily betray their brethren to improve their position.
There are various flavors of spyder-fiends, each with its unique talents for mayhem and place in the hierarchy, but their overall goal remains aligned with Miska's: to spread chaos and destruction wherever they crawl.
The Spyder-Fiend's Hierarchy

Kakkuu Spyder-Fiend
The most animalistic of the spyder-fiends, the CR 5 kakkuu are the unintelligent foot soldiers (read: cannon fodder) of the spyder-fiend ranks. They most closely resemble literal spiders with literal wolf heads, but they have enough intelligence to understand their orders and lay effective traps using their Web Snare action.
Though they are the lowest-ranking spyder-fiend, you won't likely be able to swat them with a newspaper (or maybe even a Fireball). They have advantage on saving throws against spells and other magical effects and resistance to common elemental damage types, so you'll have to be smart about what you throw at them.
Phisarazu Spyder-Fiend
The phisarazu spyder-fiends are the next step up on the totem pole, but it's quite a significant jump. Coming in at CR 13, these nasty Fiends have all the defenses of their kakkuu cousins, plus resistance to Bludgeoning, Piercing, and Slashing damage from nonmagical attacks. They also have a heap more hit points and a couple dastardly abilities.
Their Scintillating Spray causes them to expel (yuck) a cone of bedazzled webs that reveal creatures with the Invisible condition and can leave creatures within the vicinity Stunned. They can also change their shape, but only into other 10-legged creatures, like driders or crabs. This might be the first time you've been warned to be careful of crabs—unless you've been to Baldur's Gate.
Quavilithku Spyder-Fiend
The two aforementioned spyder-fiends are vital in large-scale assaults and infiltration, but the CR 17 quavilithku are where things start to get tactical. These spyder-fiends are highly intelligent and can quickly size up a foe to determine their weaknesses using their Assess Weakness Bonus Action.
But just because they get to boss other spyder-fiends around doesn't mean they can't dish it out. Their most dangerous weapon is their Dissolving Web, where they spew (yuck) a wide net of acid-drenched webs that damage creatures and objects alike. This ability synergizes well with the quavilithku's penchant for destruction, where the more beautiful the thing they destroy, the better.
Raklupis Spyder-Fiend
At the top of the spyder-fiend pecking order sit the CR 19 raklupis. These guys are the opposite of the "ugly duckling" of the bunch. In fact, they're described as having strong arms, alluring voices, and luxurious fur, so they might even be considered "majestic ducklings."
But, despite their good looks, these are the most dangerous combatants spyder-fiends have to offer. They can cast some pretty nasty spells, including Dominate Monster and Mass Suggestion, and can snap their subordinates out of the Charmed and Frightened conditions with their Demand Loyalty ability.
Spyder-Fiends, Spyder-Fiends...
The four subspecies of spyder-fiends analyzed in this article are only a portion of over 30 monsters included in Vecna: Eve of Ruin. Since this adventure takes characters from levels 10 to 20, it's safe to assume that dangerous foes will be lurking around every corner.
To help run these deadly encounters, Master-tier subscribers who purchase Vecna: Eve of Ruin on D&D Beyond can use the book in Maps. This VTT helps Dungeon Masters prep their games by integrating with their D&D Beyond library, so they can populate their virtual tabletop with all the maps and monster tokens from the book. Then, when it comes time to roll for initiative, they can invite their players and use features like fog of war and measuring tools to help them run their games!

Mike Bernier (@arcane_eye) is the founder of Arcane Eye, a site focused on providing useful tips and tricks to all those involved in the world of D&D. Outside of writing for Arcane Eye, Mike spends most of his time playing games, hiking with his partner, and tending the veritable jungle of houseplants that have invaded his house.
Out of curiosity: what, specifically, has been spoiled for you?
cool monsters, they should add a feature where you can buy just the monsters from a book. oh, wait.....
google works at least
I haven't read this one but they had the chardalyn dragon on the Beyond front page for a month after Frostmaiden came out. With just the headlines of the articles I could probably story board Vecna already. I never read the articles and get enough spoiled just trying to log in and get to my campaigns.
doge spooder dmemon
also it says they have a hierarchy, but their demons and demons are CE not LE therefore they should have no hierarchy and should just be "im the strongest so u do what i say or u die". i guess that theres the whole demon princes and their domains and stuff but still i dont really think they should be calculating or have a hierarchy given that their demons.
I have an arachnophobic player who’s taking on eve of ruin. I can’t wait to unleash Miska upon them. Maybe then they’ll regret using their so called “Optimised Builds”.
I don't believe we've seen these in any official release in over 20 years, nice to see them again. But I think that I preferred the more wolf-like head on them, from back in AD&D.