Taint

Taint is a horrific corruption of the land, the physical manifestation of chaotic magic twisting the life of the Overworld.

It is a multilayered affliction, affecting the landscape as Tainted Land, and the player as a Taint status effect. Tainted lands show a dramatic purplish coloration, with plants and trees visibly decaying. The status effect causes occasional damage to a player or mob. If a mob dies while affected by the Taint status, it will be reborn in a twisted form (see below).

Creation and Cures
Some tainted areas are created during world generation, either directly or by way of a Tainted Node. Natural Tainted Lands often appear next to Magical Forests, and may spread into them (small areas will be protected by node-bearing silverwoods).

They can also be created by the player, most often as a result of producing large amounts of Flux and failing to clean it up. Also, the primal focus can rarely create fibrous taint. In creative mode, tainted creepers or tainted sheep (see below) can be used to spread taint, as both creatures produce fibrous taint.

Tainted areas can be healed or blocked from spreading, by "pure nodes" (notably those produced by silverwood trees), or with an Ethereal Bloom.

Behavior
Tainted areas tend to spread over time, but slowly. Tainted nodes convert the area around them, but otherwise taint spreads only via fibrous taint, which is blocked by water. However, tainted sheep or creepers can produce fibrous taint (as can pools of flux goo, or, rarely, a Primal Focus). While the taint affects the whole vertical range, it spreads only by fibrous taint, and even in a tainted area, not all blocks may be tainted. A tainted area often extends further underground than the visible corruption on the surface.

A tainted area can be fairly forbidding, starting with the purplish discoloration of land, water, and even sky. Any life that was there before will be infected: Tree trunks will become Crusted Taint (and slump to the ground), while most other plants will become Fibrous Taint. Eventually, even the Crusted Taint will decay into flux goo.

Mobs entering or spawning in the area will be converted to tainted versions or to Thaumic Slimes, and there are several unique monsters found as well, notably the grotesque Taintacle. The player will also be affected -- when passing over tainted areas, they will occasionally suffer a few seconds of the Taint status effect, which may cause damage or other effects.

The spread of taint can be limited with a option in Thaumcraft's config file; if taint spread is disabled, any existing taint will continue to fill in the infected chunks, but will not spread beyond them. Even with normal spread, taint quickly fills in chunks, but beyond that, is slow to expand into new areas. However, tainted sheep or creepers can spread the taint further, as can flowing flux goo from corrupted trees.

Taking souvenirs is tricky: Tainted dirt, stone, etc mine as normal materials, and fibrous taint drops nothing. However, Silk Touch will let you harvest Crusted Taint and Tainted Soil, and some of the monsters do drop remains (tainted goo and taint tendrils). However, getting them home is non-trivial; when carrying either item in your inventory, each 45 seconds one of the items will decay, infecting you with taint for 45 seconds. However, tainted relics can be stored in a chest, ender chest, or in a traveling trunk, or tossed through a magic hand mirror into storage. If stored in a donkey or mule's pack, they will not decay or harm the animal, but a tainted biome is not a safe place for such beasts! Having been collected, taint drops can be distilled for Vitium essentia, which is required to create Ethereal Blooms (or Bottled Taint). Formerly, they could also be gotten to storage by playing "hot potato" with them, tossing them on the ground and picking them back up every 30 seconds or so. However, the current version seems not to reset the timer when items are dropped, so that "hot potato" doesn't work anymore.

It is best to be wary of taint: move your base if taint is spreading towards it, or use a taint-clearing strategy to choke off the taint. Similarly, be sure to clean up any pools of flux goo resulting from crucible overflow, infusion instability, Warp, or other magical accidents.

Mobs

 * Tainted mobs -- Most untainted mobs will be "killed" by the taint, but instead of dying, they will be converted either to a twisted version of their former selves (stronger, and more aggressive), or to a Thaumic Slime. By species:
 * Zombies, skeletons, and slimes are unaffected, though they may get into fights with Taintacles. Endermen will simply teleport away, and will also be unaffected.
 * The usual farm animals (pigs, sheep, cows, and chickens), and also villagers, become tainted versions of their type, which are hostile (and will also attack untainted mobs). Naturally, their new attack inflicts taint on the victim. Note that tainted sheep can spread taint -- everywhere they stop to "graze", they will leave tainted soil behind.
 * Creepers will not be attacked by most monsters (Taintacles can set them off), but will eventually be killed by the ground effects, and converted to a tainted form. When these explode, the entire blast radius will be tainted.
 * Other mobs such as horses, wolves, and spiders, have no tainted form, and will become Thaumic Slimes. (Sometimes big ones!)
 * Taintacles: These disturbing creatures grow out of the ground. While their base is fixed in place, they continually lash out at creatures around them. They can get in fights with untainted monsters, and also attack each other (which effectively enforces a minimum spacing among them). They can also attack opponents who are otherwise out of reach, by spawning several small Taintacles under their feet.
 * Swarm Spawners: These appear as a block of taint interleaved with evil light. They produce Taint Swarms when a player is still a considerable distance away. Despite their blocklike appearance, they are in fact mobs; when struck, they will flash red and take damage, They have 35 hearts of health.
 * Taint Swarms: These glowing swarms of purple lights attack all passing players, and can fly up to attack those whothought their Thaumostatic Harness kept them safely out of reach. Despite the swarm's immaterial appearance, it can be attacked with a weapon in the usual fashion. They have at least 10 hearts of health, and possibly up to twice that.
 * Tainted Spores: These fleshy-appearing blocks will shower purplish particles when approached, then once a player comes within 3-4 blocks, burst into a group of Tainted Crawlers. They will likewise burst if placed (creative mode) on non-tainted ground.
 * Tainted Crawlers look like tiny purple spiders with the typical tainted look. They have 2.5 hearts of health and deal 1 heart of damage when they attack.
 * Thaumic Slimes: Similar to the familiar slimes, but these are more aggressive, faster, and generally larger. They split when killed like ordinary slimes, but they can also merge with each other. In older versions, they could grow by absorbing liquid flux, but this has been nerfed as of 4.2. Unlike typical slimes, all sizes of Thaumic Slime do 2 hearts of damage and have 13 hearts of health, making all sizes equally dangerous