Permadeath
Permadeth means that when one of your characters dies inside the game, he is gone for good. Save files exist only as a device to allow you to play a single game across multiple sessions sessions, but they are deleted once your character dies.
Permadeath is one of the main features of roguelikes; it encourages you to take your decisions wisely and to make strong bounds with your character, as you must defend his life if you want to be sucessful in the game.
Permadeath is not as bad as it would seem at first...