Data: fat; small; tall fat: "tall is Life" small: "tall is Death" tall: "tall is Dungeon" Reasoning: tall is Life, Death or Dungeon. He can't b

Data: fat; small; tall fat: "tall is Life" small: "tall is Death" tall: "tall is Dungeon" Reasoning: tall is Life, Death or Dungeon. He can't be Life, because if he was, he would have said he was. So he's Death or Dungeon. Now, one of the other two must be Life (because tall isn't), and so one of them must be telling the truth about tall. He's called Death and Life, so he must be one of them. We know he can't be Life, so tall is definitely Death. Whoever called him Death was telling the truth, and must be Life. Only small called him Death, so small is Life. (edit I should have said: Life must be telling the truth about him, so if only one of them does that, that one is Life). And the remaining guy - fat - must be the remaining knight - Dungeon. Dungeon can lie or truth, so it doesn't matter what he said (in fact, he was lying: he said tall was Life, when tall was Death). It only mattered what he said so we could distinguish between him and small. fat is Dungeon small is Life tall is Death Took about a minute. I had to draw a diagram to track the details - my evolution includes pen and paper. :-P