|This feature is exclusive to Java Edition.|
The Village & Pillage update overhauls the trade system, bringing with it many new ways to gain emeralds from villagers. Villagers themselves adjust their trade prices depending on the player's behavior with them. There is one particular behavior that the player can do to potentially gain infinite emeralds from a single villager, detailed below.
The main way that villagers determine their prices for a specific is through hidden "gossip" tags stored in their NBT data. There are five distinct gossip tags related to trading;
trading. The main gossip tag that allows for potential infinite emerald exploits is the
major_positive tag, which can only be gained by curing a zombie villager; unlike other gossips, major positive gossip cannot be shared, and only the villager that was cured can have the tag. Villagers with major positive gossip towards a player heavily discount most of their trades for the player in question; these discounts are permanent, though can be affected and temporarily nullified by negative gossip.
Some villagers have trades in their lists that are related to each other; in particular, librarians. Novice-level librarians have a chance to sell 3 bookshelves for 6 emeralds, and Apprentice-level librarians have a chance to buy 4 books for 1 emerald. Normally, this ratio is such that it is not possible to make a profit by buying bookshelves, breaking them, and selling their book drops back; however, villagers with major positive gossip can discount their trades enough for it to become quite profitable.
What you'll need
- At least one lectern
- One zombie villager
- One golden apple
- One splash potion of Weakness
- At least 10 emeralds
- Some building blocks
Note that this process is dependent on RNG; you may need more emeralds and another villager (possibly even 2 or more if you're especially unlucky) if RNG does not work in your favor.
First, find and cure a zombie villager. Information on this process may be found here.
After curing the zombie villager, trap it in any sort of structure that protects it from mobs and prevents it from escaping. Once trapped, place down a lectern next to it so that the villager may become a librarian. Check its trades to see if it sells bookshelves; if if does not, break the lectern, wait for the villager to lose its librarian profession (visible by it losing the librarian uniform), and place the lectern down again. Check its trades again; if it still does not sell bookshelves, repeat the process until it does. Be careful to not trade with the villager until it sells bookshelves, otherwise the process may have to be restarted from the beginning. (You may optionally keep rerolling the librarian like this until you get a decent enchanted book trade alongside the bookshelves, but this is not necessary.)
Once the villager sells bookshelves, lock in its profession by trading with it. Normally, librarians sell 3 bookshelves for 6 emeralds, but cured librarians discount this trade for it to be 3 bookshelves for 1 emerald. Keep buying bookshelves at this discounted rate until it levels up from a Novice to an Apprentice - it should take 10 trades total.
A note about RNG
At this stage, RNG kicks in some more. Apprentice-level librarians have a 2/3 chance to buy 4 books for 1 emerald, though cured villagers discount this to 1 book for 1 emerald; if you're lucky, your cured librarian will also buy books and you can get started on gaining infinite emeralds. If you're not so lucky, however, you will need to get another villager (it does not have to be cured, but the process will be much more profitable if it is), make it a librarian, and level it up to Apprentice. If the extra librarian still does not buy books at Apprentice-level, keep making more librarians until one does.
How to make quick profit
Once you've got your cured villager selling you discounted bookshelves and a way for you to sell books, you can start turning a profit quickly. Place down the bookshelves and break them with any non-Silk Touch tool (an axe is quickest). Each broken bookshelf drops 3 books. Once you've gotten all your books, sell them back to the librarian(s).
- If you've got an all-in-one cured librarian (one that sells bookshelves and buys books), or two cured librarians that can sell shelves and buy books at discounted rates, the process works out to buying 3 bookshelves (9 books) for 1 emerald, and then selling 1 book for 1 emerald, resulting in a profit of 8 emeralds for every bookshelf trade.
- If you have a cured librarian selling bookshelves and a normal librarian buying them, the process works to buying 3 bookshelves (9 books) for 1 emerald, and then selling 4 books (at base price) for 1 emerald, resulting in a profit of 1.25 emeralds for every bookshelf trade. However, the normal librarian can lower its prices as a result of gossip, making the process more efficient.
You may repeat this process as often as you like; the cured librarian(s) will not raise their prices on you, assuming you don't go attacking them or other nearby villagers. Assuming the librarian(s) always have access to their lectern(s), you can easily make several emerald blocks worth of profit in a single in-game day. You can make this process even faster and more profitable by curing more and more zombie villagers and making them librarians, to get around the restocking delays.