Arachnomorphs (called monstrous spiders by simple folk)[1] are large insectoid creatures resembling spiders. They are post-Conjunction creatures, and their preferred choice of habitat is a deep, damp cave or the occasional isolated swamp.
While they don't appear in the base game, they do appear in both its expansions: Hearts of Stone expansion and Blood and Wine expansion.
The spider shall never lie down with the fly. – Ofieri proverb
A similar saying could gain ground in our land concerning arachnomorphs and everything unable to flee them – meaning most every creature in the world. True, the tillers of the earth and fellers of trees need not fear them in their daily labors, for arachnomorphs, as distant, post-Conjunction cousins of common spiders, strongly prefer deep, dark caves and unfrequented sodden swamps. Anyone who does come across them, however, had best hope his conscience is clear and his worldly affairs are in order, for his life shall soon end, as not even the fastest man in the world can outrun them and only a few witchers can hope to slay them. Even worse are the more aggressive and dangerous kind known as arachnomorph colossi, which are capable of devouring an entire ox in seconds.
When fighting these creatures the rule of thumb is to stay mobile, while this applies to fighting all monsters the spiders have the ability to spit webbing that can stop the player in his/her tracks, leaving him/her vulnerable to further attack; they always charge in for a hit while you're tangled in the webs. The spiders attack as one when the odds are in their favor, but when the player starts to attack they retreat at quite a surprising speed leaving the player frustratingly out of reach, spitting the webbing whenever they can. This is one of the most effective uses of in-and-out guerrilla warfare seen by any monster type, so your main goal will be to slow them down one-by-one to hit them while dodging the attacks and web shots of the others.
Yrden is arguably useful, for it slows arachnomorphs, though area of the sign is much smaller than arachomorphs "playground".
Igni can set the creatures alight and buy yourself some time to combat the rest. If started at very close range the Whirl attack can usually keep smaller arachnomorphs off-balance enough to constantly keep them in range until dead (the Severance Runeword greatly helps with this) however the big ones will usually be able to jump out of range or counterattack you and stop your attack.
Aard and Axii are also useful to disable the spiders so you can close in the for the kill, though be wary of unstunned spiders closing on you while you try to dispatch other targets. The bio for these spiders says they like caves, yet while venturing in the world they can be encountered in forests. One should also not dismiss Quen sign as it blocks webbing hurled at the witcher, preventing the dangerous entanglement.
Most useful tactic (on Broken bones, NG+ with upscaling) is combination of Aard Sweep, Active Shield (prevents entaglement/root) and high mobility (dodging). Sidestep creature that attack and follow up with a few quick attacks before it runs of. Refrain from chasing a single foe and fight them as a unit. As stated before, arachnomorphs are most organised group fighting monster type in the game.
