The Legendary Titles

The Last Key Door is an indestructible block that cannot be broken by any means -- not even explosions -- unless you possess the Last Key. Right-clicking the door will display a message telling you whether you hold the key, no key has been claimed yet, someone else holds it, or the key has been permanently lost. When you first place a Last Key Door in the world, you are granted the one and only Last Key that will ever exist. Guard it with your life -- if you die while carrying it, the key is destroyed forever. Once lost, every Last Key Door in the world becomes permanently and irreversibly sealed, so treat it as the most precious item in your game.