You can’t name Sting until you have killed a spider. (This could be limited to after you kill a giant spider, but by that point most players probably don’t need Sting.)

Potion of bug repellent; is poisonous or otherwise harmful to drink, but if you smash it over yourself, all insects (classes a, s, and x) will flee from you.

Spider nest room; a zoo-type room (where every square generates a monster independently) with giant and cave spiders. Each square additionally has a 70% chance of a web. Loot consists of several “bones piles” that have a few random objects but no comestibles.

When the player kills a giant spider with an elven dagger and Sting has not yet been created, the dagger is converted into Sting automatically. Sting is made of rustproof steel, instead of wood (this would be tricky to do because of base items; you would still want to be able to create it by naming an elven dagger, but Sting in the lore is made of steel or at least metal, not wood). Sting has bonuses versus spiders, in addition to its bonuses against orcs.

Spiders have an attack that wraps you in a web (using sticky attack behavior?) or creates a web on your square and traps you in it, so you can’t move.

See also #1409, which discusses a similar idea where spiders can do this sort of thing at range.

Spiders can spin webs as they move along (cave spiders with less frequency than giant spiders.) This chance is boosted if they move into a doorway or choke point.

New monster behavior flag M2_CLIMB or M3_CLIMB: added to monsters that are natural climbers (spiders, ants, most Y) and with effects like being able to get out of a pit in one turn, or who can climb up ladders without having hands.

Stomping boots. While wearing these, you may instakill and move into the square of all small monsters in the a, s, and x classes.

Electric spider that, when it stands on a web, can electrify that web and all contiguous ones, dealing shock damage to anything in it.