Fermented Spider Eye

The Fermented Spider Eye is a potion ingredient used to brew potions with negative effects aside from the Potion of Invisibility. It can be crafted from a spider eye, brown mushroom, and sugar on a crafting grid. They are inedible, unlike the regular spider eye.

As drinking any potion with a negative effect yourself is quite a silly thing to do, the potions are often brewed into a splash potion with gunpowder, making them throwable weapons that inflict their effects on mobs/players instantly. However, throwing the potion too close causes the player to suffer from effects too.

Crafting
The items needed can be put in any shape.

Bugs

 * Sometimes, Spiders may drop Fermented Spider Eyes instead of Spider Eyes. This is only known to occur in snapshot 12w38b.

Trivia

 * Fermented spider eyes corrupt the effects of a potion they're used on.
 * Undead mobs, mainly zombies, skeletons and zombie pigmen, are actually healed when hit by a potion with instant damage. Inversely, attacking them with a healing potion makes them take damage.