Phantom Membrane

Phantom membranes are obtained from killing phantoms.

Mob loot
Phantoms drop 0–1 phantom membrane when killed by a player or tamed wolf. Looting increases the maximum drops by 1 per level, for a maximum of 4 with Looting III.

Cat gifts
Tamed cats have a 70% chance to bring the player a gift when they wake up from a bed, and the gift has a 3.22% chance to be a phantom membrane.

Repairing
Phantom membranes can be used in an anvil to repair elytra, restoring 108 durability points (25% of the pair's total durability) per membrane while preserving their enchantments.

Brewing ingredient
Phantom membranes are used to brew slow falling potions from an awkward potion.

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