Bed

Bed does three jobs, and sleeping is only the first. Sleeping in a Bed skips the night and any thunderstorm, sets your respawn point, and clears the phantom timer that has been counting since the last time you slept — go three in-game days without one and phantoms start arriving after dark.

The respawn half is where worlds get lost. Your spawn point survives only as long as the Bed does: break it, let a creeper take it, or wall it in so tightly that there is nowhere to stand, and the next death drops you back at world spawn with nothing but a chat line to explain it. A spare Bed in the pack, and a second placed at any base you use often, is cheap insurance.

Beds are also how a village counts itself. Villagers claim a Bed as a home and will only breed while an unclaimed one is within reach, so the number of beds — not doors, not villagers — sets the population ceiling. Adding beds is how a trading hall grows and taking them away is how you stop it.

In the Nether and the End a Bed does not put you to sleep, it detonates. That is a tool once you expect it: bed blasting is the cheap way to clear netherrack around ancient debris, since the explosion costs wool rather than TNT, and it wants a block between you and the blast every time. Beds come in every dye color, take up two blocks of floor, and refuse to work at all while a hostile mob is close enough to notice you.