Eye of the Void

Eye of the Void is a trinket that can be bought from Stranger, acquired from the Trinket Loot Table, or as a general drop found inside Stronghold chests. When carried in the inventory, it allows the player to occasionally acquire ender pearls from killing mobs(excluding farm animals). Every 6 mob kills grants a 37.5% chance at an ender pearl.

As stated in the item's in-game description, placing the banner as a block will cause it to stop working entirely, even if the item is retrieved, as the tags that make this item work are deleted once the item is placed as a block.