My brain basically broke it down like this: 1. Anyone saying someone else is the knight of life must be either the dungeon or the death. i. If the person he said is the knight of life, calls himself the knight of life then things get complicated... ii. Luckily the person that was called the knight of life, in fact called himself dungeon, which means that neither could be the knight of life. 2. Since the knight of life is the small, believe what he says. The tall = death. 3. This leaves only the Fat to be paired with the dungeon.

Fun puzzle.