Lethal: At 0 Health Points you are at negative Health points and must roll from the negative effects chart. You must make a save each round or fall unconscious. If unconscious you still continue to roll to regain consciousness. Main Ability (100%) Each additional critical Health against you requires you to roll from the chart again.
Non-Lethal: At 0 Health points you are surrounded by a strange glow that makes it difficult to act. (-10 attack / -10 AC) At 0 Stike Points you must make a save each round or be captured (assuming the enemy has a capture gem). Main Ability (100%) Each additional critical Health against you requires you to roll or be captured again.
Death: At 600 Negative Health points a character is dead and can only be revived through intervention by a deity.
Note: Deities rarely intervene unless there is an extremely compelling reason and even then have been known to ignore these requests for reasons beyond mortal understanding.