The Reasoning

The Condition Track is, quite simply, genius. D20 suffers from a multitude of conditions. Some of them are quite unique and useful, but many are just difficult-to-remember penalties. Because of this, they aren't used nearly as often as they should be. (Without looking at your books, what's the penalty for being Dazzled? How long does it last? When's the last time you even used Dazzled?) The Condition Track unifies these nothing-but-penalty conditions into a single, simple ruleset with easy rules.

As well, it allows the creation of "HP levels" that makes sense and is actually easy to use in-game. Many people like the way HP works in general, but are bothered by the edges of the abstraction, where a character with 200 HP can take 199 damage and still fight at full capacity. The Condition Track allows you to model exhaustion and shock due to damage during a fight without having to do any math or keep track of varying numbers.

The Rules

Anytime you receive damage higher than your damage threshold, you go down one level on the Condition Track. Other actions may also move you down the Condition Track. You may recover by one level by spending three swift actions. These do not have to be consecutive - you can spread them out over several rounds.

Level 0: No change. This is the default condition.

Level 1: -1 to attacks, defense, saves, and skills

Level 2: -2 to attacks, defense, saves, and skills

Level 3: -5 to attacks, defense, saves, and skills

Level 4: -10 to attacks, defense, saves, and skills. Movement reduced to 50%.

Level 5: Unconsciousness/death.

A creature reduced to 0 hit points moves -5 steps on the condition track and falls unconcscious. If the attack that drops you to 0 hit points also exceeds your damage threshold, you're dead. There are no negative hit points. You're either dead or unconscious. (If you use Action Points or a similar variant rule, spending one to avoid death in this manner is an appropriate use. Saga lets you spend Force Points to do so.)

If you fall unconscious, you fall prone and can't take any actions. At the end of the encounter, you make a DC 10 Constitution check. If you succeed, you move +1 step on the condition track, regain consciousness, and recover hit points equal to your level. If the check fails, you remain unconscious for 1 hour, after which you can attempt another Con check. You can make a new check ever hour until you regain consciousness.

If you fail by 5 or more points, or roll a natural 1 on your check, you're dead. Obviously, you aren't allowed to take 10 on this check. You do not take any penalty to this check (as level 5 on the Track grants no penalties beyond unconsciousness). In addition, if you've failed a Con check to regain consciousness, your condition is considered Persistent (more on that below). Regaining consciousness will still move you back to Level 4, but you can't recover further without rest or medical attention.

Any character may make a DC 15 Heal check to stabilize you, allowing you to immediately regain consciousness as if you had succeeded at the Con check. Your condition is still Persistent if you've failed a Con check before receiving healing.

If you're suffering from a Persistent Condition, you can't use the recover action to move up the condition track, and you can't regain hit points naturally. Persistent conditions can be removed only under certain circumstances. Persistent conditions resulting from injuries require surgery, healing, or 8 hours of rest. Diseases have to be cured, poisons treated, et cetera.