Anvils and Combining Enchantments

An anvil is crafted from 3 blocks of iron across the top row plus 4 more iron ingots below, 31 iron ingots in total, a serious investment for what it does. It repairs items, renames them, and does something an enchanting table alone can't: combine enchantments from two separate sources onto one item, including moving enchantments off a tool entirely and onto a fresh replacement.

Combining two matching tools (say, two iron pickaxes) repairs the target: it adds the sacrifice item's remaining durability plus a bonus of 12% of the maximum, capped at full, and merges both items' enchantments onto the result. Combining a tool with a matching enchanted book instead only merges enchantments — there's no durability to add, since a book doesn't have any. Two books carrying the same enchantment at the same level merge into the next level up (two Sharpness IV books make Sharpness V), up to that enchantment's own cap.

Every operation an item goes through on an anvil adds a hidden "prior work penalty" that roughly doubles each time — 0, 1, 3, 7, 15, 31, and so on — stacking on top of whatever that specific operation actually costs. In Survival mode, any operation that would total more than 39 experience levels is simply refused, with a "Too Expensive!" message, no matter how many levels you actually have banked. A heavily reworked item can hit that wall after only a handful of anvil visits, even for something as cheap as a rename. The fix is to plan ahead rather than repair carefully: merge your enchanted books together first, into one combined book, then apply that single book to a fresh, never-touched tool in as few operations as possible — fewer, bigger merges cost less in total than many small ones.