Poison is a dark purple liquid block found in Poison Forests, it is dangerous but not like lava.
When standing in poison, the player will not take damage normally, but if the player is injured, has a 20% chance to get poisoned with poison 1 (open wounds are susceptible to poison). However, when the player's head is submerged, they have a 50% chance of receiving poisoning if uninjured, and 1n 80% chance if injured.
Poison can be obtained in a bottle, and can be crafted into a splash bottle of poison. A bottle of poison has a 100% chance of poisoning the player, while a splash bottle of poison only has a 20% of poisoning anyone who it hits. both bottles have a 0.8% chance of giving the player Poison II for 10 seconds, the same percentage of a spider jockey spawning.
In brewing, poison bottles act as water bottles, but by default switching to the negative effect, and automatically making a Poison II potion instead of a Poison I potion. Even though poison bottles can be crafted into splash bottles, potions made from the ordinary bottle still require gunpowder to become splash potions.