BeginnerEnchanting & brewing
Potion brewing in Minecraft: every recipe in one place
The exception is the Fermented Spider Eye:
Tested 26.3
Item
Fermented Spider Eye item in Minecraft
A Fermented Spider Eye corrupts potions, turning them into their harmful or opposite version.
It is made with the Crafting Table from Spider Eye, Brown Mushroom and Sugar.
What it does
Craft it from a Spider Eye, a Brown Mushroom and Sugar. Added to a potion it changes the effect: swiftness becomes slowness, healing becomes harming, night vision becomes invisibility, and a water bottle becomes weakness.
How to craft
Crafting table Any arrangement Also in the 2×2 inventory grid 
Spider Eye + Brown Mushroom + Sugar → Fermented Spider Eye
// Slots with several items cycle through every accepted option.
How Fermented Spider Eye connects
10 links · from the 26.3 game dataTurns into
+
Potion of Night Vision → 
Potion of Invisibility +
Potion of Swiftness → 
Potion of Slowness +
Potion of Healing → 
Potion of Harming Trades
Wandering TraderBought bySame family
Spider Eye
Eye of EnderTutorials with Fermented Spider Eye (2)
BeginnerVillagers
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In a Brewing Stand fuelled with Blaze Powder, add a Fermented Spider Eye to a Water Bottle to get a Potion of Weakness (no Nether Wart needed), then add Gunpowder to…
Tested 26.3
Fermented Spider Eye · FAQ
How do you get Fermented Spider Eye in Minecraft?
At the Crafting Table: 1 × Spider Eye, 1 × Brown Mushroom and 1 × Sugar give 1 × Fermented Spider Eye. Bought by Wandering Trader.
What is Fermented Spider Eye used for in Minecraft?
It corrupts potions into their negative versions. Brewing: it turns potions into Potion of Harming, Potion of Invisibility, Potion of Slowness and Potion of Weakness.