Hardcore

Hardcore mode is a new difficulty mode that is set to be released in the Beta 1.9 (or possibly 1.10) update. The mode is set from the world generation page and can be toggled on and off.

Hardcore mode deletes the world when the player dies.

While playing in hardcore mode, the game is locked to hard difficulty.

The idea came to Notch from a Minecraft gameplay blog on the PCGamer site.