Requires the library mod Collective.

This mod is part of The Vanilla Experience modpack and Serilum's Spawn Bundle mod.
Cave Spider Spawn adds a chance for cave spiders to spawn naturally in place of a normal spider. By default they have a 15% chance to spawn and only below the surface, though this can be changed in the config. Adds a bit more difficulty to the game, due to cave spiders being able to poison players and they're harder to hit.

It's also possible to make cave spiders only spawn below a certain Y level. For example below y=0, which is where deepslate is. This is disabled by default, and can be toggled in the config.

Configurable: ( how do I configure? )
chanceSpiderIsCaveSpider (default = 0.15, min 0, max 1.0): The chance a spider that has spawned is a cave spider.
onlySpawnCaveSpidersBelowSurface (default = true): When enabled, cave spiders will only spawn below the surface.
onlySpawnCaveSpidersBelowSpecificY (default = false): When enabled, cave spiders will only spawn below the specific y value set in 'belowSpecificY'.
belowSpecificY (default = 0, min -1000, max 1000): The specific y value used in 'onlySpawnCaveSpidersBelowSpecificY'.

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You may freely use this mod in any modpack, as long as the download remains hosted within the CurseForge ecosystem.

Serilum.com contains an overview and more information on all mods available.

Comments are disabled as I'm unable to keep track of all the separate pages on each mod.
For issues, ideas, suggestions or anything else there is the Github repo. Thanks!