INK SAC

Every other dye starts as a plant or a mined block. This one starts as a squid: nothing crafts an ink sac, and the only way to get one is to kill the animal that carries it in open water. A Librarian buys it off you at journeyman, paying 1 emerald for every 5 handed over.

1 ink sac becomes 1 black dye on a crafting grid, one for one, so an inventory of ink sacs is an inventory of black dye that has not been crafted yet. Selling raw sacs to the Librarian and buying black dye elsewhere is rarely the shorter path; the ink sac usually is the finished ingredient.

There is no farm for it in the way there is for cocoa or lapis. A squid pool near a riverbank or an ocean shoreline is the entire supply chain, one kill at a time.

One profession takes it. Bring it to a Librarian once he reaches journeyman, and he pays 1 emerald for every 5 sacs handed over, the same rate no matter which librarian you ask.

The best rate any villager offers is an emerald per 5 ink sacs, from the Librarian, and 2 of the other 3 pay out faster. No villager sells ink sac back, so it is emeralds out and nothing in.

One slot at the Librarian takes 5 ink sacs a trade, 12 trades, 12 emeralds. 8 of the 72 villagers that pay emeralds, emptied out:

12 acacia boats against 288 flint for the same 12 emeralds, 24 times the carrying, and the shortest wait is the Butcher at 7.5 real minutes of shelf, gathering not counted. Ink Sac itself pays 5 an emerald, so 22 of the 72 ask less and 49 ask more.

Place a lectern next to an unemployed villager and he becomes a librarian, though this offer is not there from day one. It sits at journeyman, so he needs to trade his way up through the earlier tiers before ink sac shows up on his sheet at all.

Once it does, the slot buys 12 sacs before it locks, and a restock brings the same price back rather than a fresh roll, so a librarian who buys ink sac keeps buying it every time the offer refills.

12 sales close the slot, and the lectern needs 2 real minutes before the librarian can refill it. A Minecraft day runs 20 real minutes, long enough for two of those refills to land while you wait.

One librarian absorbs 120 ink sacs across a full day, which is a lot of squid for a single dye color, and worth weighing against just farming cocoa or another plant dye for anything that does not specifically need black.

Fight over open water, not a pond. Squid need room to spawn and swim, so a coastline or a river bend produces more of them faster than a small dug-out pool ever will.

Where they go back: that Librarian also sells lanterns at 1 emerald each, its cheapest offer.

Also on the Librarian's list: glass, book and quill, clock, compass, yellow candle, and red candle, the rest of what one lectern can put on offer.

Squid drop ink sacs, and that is the only common source of black dye in the game. No flower gives it, which is why a builder far from water either travels for it or buys it.

Ink also writes: a sac with a book and a feather makes a book and quill, and with bone meal it makes grey. The glow squid's version does something else entirely, turning a sign's text luminous, and the two are not interchangeable.

An ink sac and a feather turn a book into a book and quill, which is the only way to write anything in the game longer than a sign.

On a sign an ink sac does the opposite of what you would expect: it darkens the text back to default after glow ink has been used on it. Glow ink comes from a glow squid and makes a sign readable in the dark.

As a dye it is black, and mixed with bone meal it gives grey, so a squid pond is two colours rather than one.