Anvil

Anvil is where enchanted gear gets maintained. It repairs items without stripping what is on them, merges two enchanted items or books into one stronger result, and renames anything you put in it — the only survival way to name a tool or write on a name tag. A grindstone also repairs, but it deletes every enchantment while doing so, which is what makes an Anvil worth its iron.

The cost is levels, and the cost grows. Every operation stamps a hidden prior-work penalty onto the item that doubles with each later use, so the order you combine things in decides what you can still afford. Merging books into each other first and applying the finished book to the tool last is far cheaper than adding them one at a time. In Java Edition the Anvil refuses any operation priced at forty levels or more and shows Too Expensive instead; an item at that point still works, it just cannot be modified again.

Repairs take either matching raw material or a second copy of the item, and merging two worn copies returns their combined durability plus a bonus, which rescues a nearly dead tool without an ingot. Mending sidesteps the system by paying with experience as you collect it, which is why a well-enchanted pickaxe may never need an Anvil again.

The block itself wears out. Each use carries a chance to chip it, and it degrades through two damaged stages before shattering — and no, a damaged Anvil cannot be repaired; you craft a replacement. It also obeys gravity: knock out the block beneath one and it falls, hurting whatever it lands on — a deliberate trap and mob-farm technique rather than a bug.