Poison! is an attack contact effect which provides a temporary medium 
armour-piercing missile damage, 
armour-piercing weapon damage, 
base missile damage, 
base weapon damage 
speed and 
vigour 
debuffs to an enemy unit when hit. It is the classic weakening attack effect in the Total War: Warhammer game series. Attacks imbued with Poison! are said to be poison attacks.
As a contact effect, it only triggers when the blow is successful and actually lands on enemies. However, as long as the attack is successful, poison will always trigger, cannot be negated by resistances of any sort, does not stack and can be constantly refreshed.
An attack contact effect applies to melee attack and/or missile attack so it is possible for a unit to have poison on one or both of its damage channels. It can be devastating in missile units which can slow, fatigue and ultimately weaken incoming enemy units.
References to poison usually include poison and poison! with an exclamation mark (!). The effect is called poison! and the attack is imbued with the poison effect.
Effects
Armour-piercing missile damage: -15%- Armour-piercing weapon damage: -15%
- Base missile damage: -15%
- Base weapon damage: -15%
- Poison! (10 seconds)
- Speed: -15%
- Vigour: -18%
Notable units
- Night Goblins
- Night Goblins (Fanatics)
- Night Goblin Archers
- Night Goblin Archers (Fanatics)
- Night Goblin Warboss
- Forest Goblin Spider Riders
- Forest Goblin Spider Rider Archers
- Night Goblin Squig Hoppers
- Skarsnik
- Giant Spider (Mount)
- Catchweb Spidershrine (Mount)
- Da Rusty Arrers
- The Arachnarok Queen
- Spider Hatchlings
- Deff Creepers
- Da Eight Peak Loonies
- Durkit's Squigs
- Da Swamp Fings (River Trolls)
- Feral Wyvern
- Lava Arachnarok Spider
- Lava Spider Rider Archers
- Armoured Squig Hoppers
- Crypt Ghouls
- Crypt Horrors
- All units in an army led by Helman Ghorst
- The Feasters in the Dusk
- The Konigstein Stalkers
- Morghur
- Chaos Warhounds (Poison)
- Chaos Spawn (Beastmen)
- Jabberslythe
- The Vorbergland Broodmother (Jabberslythe)
- Groghooves of Wolf's Run (Centigors - Throwing Axes)
- Glade Guard (Hagbane Tips)
- Glade Riders (Hagbane Tips)
- Giant Spiders
- Forest Dragon
- Sisters of Twilight
- Any Dreadlord with the Poisonblade or Serpentheart Names of Power
- Slaanesh's Harvesters (Doomfire Warlocks)
- Khainite Assassin
- Death Hag
- Ravagers of Rakarth (Scourgerunner Chariot)
- Stegadon and Blessed Stegadon (ranged attacks)
- Skink Skirmishers and Blessed Skink Skirmishers (ranged attacks)
- Chameleon Skinks and Blessed Chameleon Skinks (ranged attacks)
- Skink Cohort (Javelins) (ranged attacks)
- Skink Chief (ranged attacks)
- Oxyotl
- Skink Oracle
- Chameleon Stalkers
- Feral Troglodon
- The Pale Death (Feral Troglodon)
- Terradon Riders
- Pahaux Sentinels (Terradon Riders)
- Red Crested Skinks
- Red Crested Skink Chief
- Bastiladon (Ark of Sotek) (ability)
- Dread Saurian (ranged attacks)
- Shredder of Lustria (Dread Saurian)
- Amaxon Barbs
- High Queen Khalida (she also gives poison attacks to her entire army)
- Necropolis Knights (Halberds)
- Necropolis Knights
- King Nekhesh's Scorpion Legion (Skeleton Spearmen)
- Venom Knights of Asaph
- Gutter Runners (Poison)
- Gutter Runner Slingers (Poison)
- Master Assassin
- Brood Horror
- Brood Horror (mount)
Items which enable poison attacks
- Fang of Qu'aph
- Ouroborous
Legendary:
Other:
Spells
- Overcast Pestilent Breath from Skaven Spells of Plague
Followers which enable poison attacks
TWW1
TWW2
Notes
- Poison! vigour reduction increase a unit's fatigue per tick. For example, a unit engaged in combat normally gets 19 fatigue/tick. When poisoned, it's now 22 fatigue/tick.