I've decided to focus on trying to explain the Dark Avatar's origins (there are a few versions), shadow and lightbending, and a few odds and ends.

I.) The Dark Avatar's Origin

A.) Origin 1: Evil Twin Scenario

While cliche, the 'evil twin' scenario has its merits. The basic concept is that the Avatar Spirit was intended to be the perfect personification of the world. But humans are far from perfect, and as such the human spirit introduced the concept of good and evil to the world. The Spirit of the World (For the sake of naming the mother of the??Avatar Spirit, let's call it Gaia), in order to maintain it's original vision, seperated the good and evil aspects of into a pair of identical twins, each having a seed of the other's essence to maintain the balance, Yin (Evil/Dark), and Yang (Good/Light). As these two grew, Yin became ostracized from the human commnuity because he was more prone to 'evil actions' than his brother, Yang, was. As such he fully embraced his dark side and became the Dark Avatar, dedicated to destryoing the world that rejected to him. This hatred was passed down to his descendants and incarnations,?? marking early history with periods of destruction, chaos, and despair.

B.) Origin 2: The Fallen Avatar Scenario

Somewhat more likely, but more like a rip off of Star Wars, this scenario involves an incarnation that fell from his/her duties and abused his/her power to the point that faith in the Avatar was nearly destroyed. In order to save their representative, this incarnation was forcibly removed from the Avatar line, seperated from it's past and future lives to prevent corruption.

C.) Origin 3: The 'Darkness Within ' Scenario

We have seen this in the canon series when Aang demanded to know where Appa was taken in "The Desert". The distortion of the voice overlay had a very dark overtone to it. This scenario seems to be the most likely in part where Aang has an internal battle with a Dark Avatar.

II.) Shadowbending and Lightbending

In order for the series to remain fresh, you need to have new?? material to work with. After season three, the only thing left for the Avatar to do is to help rebuild the nations. Naturally, you need escalation in order to keep a series going, and in order to have an effective escalation, you need someone who can provide a significant challenge to your main protagonist. If you have a protaganist who is supposedly the only person who can manipulate all four elements, how do you challenge that? You either have someone who can also manipulate all four elements at equal or greater skill, or you have a new power that cannot be immediately handled. Therefore, I created shadow and lightbending, which are in fact the same element, aether, just of different types of Chi, positive, and negative.

In order to up the ante, so to speak, the Dark Avatar would have to have a unique form of bending to set??itself above other benders and Aang himself initially, hence Shadowbending. I believe the real world martial art this could be based on is Tien Shan Pai, the description of which can be found at this link on wikipedia.org.

As for Aang, he should learn the??opposite form of bending which does not outclass Shadowbending, but merely cancels it out, Lightbending. Lightbending could be based on the real world martial art of WingTsun, the description of which can be found at this link, from wikipedia.org

What makes these possible is that I believe the Yin and Yang of??negative and postive Chi is the true source of the bending disciplines, the crossroads, if you will. By standing in this crossroad, Aang can manipulate the 4 elements. Why can't somone manipulate the source itself, what would that look like? I figure it could like this, note that the yin yang symbol move in the same clockwise direction as the Avatar cycle:

III.) Who should be the Dark Avatar?

A.) Princess Azula

I feel Azula would make the best candidate because her perfectionist nature would allow her to learn the four elements (Air, Water, Earth, and Shadow) very rapidly, perhaps even faster than Aang did. This reduces the time gap between seasons 3 and 4 and allows for the nations to become complacent and ripe for a new conflict.

B.) 'Dark' Aang

A Dark Aang would make for an interesting internal battle, but wouldn't have much dramatic impact on the world for a whole story arc.This also smacks of Anakin/Vader.

C.) Unknown Character

Perhaps the Dark Avatar is already here, hiding behind the scenes, his/her fingers moving the pieces into position for 100 years.

OK, you said some things about how Katara and gang will be useful after the DA takes over Azula, but after they try to unite the nations, what then? Like I said in the previous topic:

If you think about it, when the Dark Avatar possesses Azula and shadowbending becomes her dominant ability, Katara, Sokka, and Toph will become obsolete. As they only??know one form of bending (and for Sokka,??only physical attacks) and even Aang, with all four forms of bending, needs to learn another form of bending (light) then they can't really do anything to help him anymore. There also seems to be a theme in the group, if you think about it: Aang knows airbending, Katara knows waterbending, Toph knows earthbending, and Sokka is the physical attacker. Who, if anyone, do you think will be the group's firebender? Zuko?

Also, Iroh's journey into the Spirit World could have given him the knowledge of lightbending and even the knowledge of the Dark Avatar. Obviously, he now has a deep appreciation for the spirits and may end up traveling with Aang to the Spirit World the teach him lightbending. Possibly, lightbending can only be used by the Avatar in the real world, but in the Spirit World, anyone who knows how can use it. And since Iroh is the only other person??(that we know of) that has ever been to the Spirit World...

Shadowbending words as a advantageous component form to Yin-Yang, if the term is used loosely.

Gantros, you said in??your theory that Sozin's Comet returned for the first time to the inner solar system in thousands of year, could be what you said is false because Sozin used the comet to begin the war 100 years ago, did the comet come close to Earth?

I still say that the idea about Shadow/Light bending as seperate forms of bending doesn't ring true for me. I can see that Lightbending could be the result of combining ideas of Airbending with Firebending. With light altering the shadows of the world. Light is one of the products of fire and lightning along with heat.

??The idea that??only a??Dark Avatar??could challenge Aang is inherently flawed. There could be hundreds of different options that could arise to challenge Aang. Dark Spirits for example. Asian mythology is covered in them ranging from the holy to the unholy. If we continue with the prison comet theory, the comet could hold a powerful dark spirit that could bring chaos to the world.

??Vampiric creatures??are another possiblity. All cultures, including Asian ones, have tales of bloodsuckers who hold many powers. The comet could act as a key or prophecy to unlease a vampire. Perhaps one that gains the power to bend elements based on the blood it drinks. (Suck a Firebender, gain Firebending.) Plus other possible powers like shapeshifting and mind control and you have a threat.

??Anti-Avatar secret societies could be a threat. Men and women that have been training to kill the Avatar could bring up conflict for a future show. Especially if it goes deeper into the history of the Avatar.

??Plus we have seen that the Fire Nation was not the only nation to cause troubles. In Kyoshi's time, the Earth Nation faced a conquor that threatened the peace. Add to that those that would be upset at the new order that most like will follow 100 years war...

??As I said, I am not in favour of Shadow and Light bending being indepedant bending forms and that the Avatar can be challenged by other things. Just my thoughts.

PS: One other thing, all of the Non-cardinal elementalbending (Air, Water, Earth, Fire) have been in fact varients on the normal bending styles. (Lightning, Plant, Sand, etc) Which makes me believe more so that any Shadow or Light Bending will be a varient of the four major schools of bending.

??Except that Yin and Yang are used in the four bending like the lightning bending (refer:Bitter Work). I am not saying that there can not be a Dark Avatar. It might be possible. The things is that from the evidence in the show all bending is boiled down to the four elements. Lightning is liked with fire, Plants are controled by water in their bodies, sand is controled by Earthbending. Heck, Cloudbending is possible with the combination of water and airbending.

??That is way I don't believe in the "Light"/"Shadow" bending as you suggested. I can see a possible Dark Avatar. I had ideas like that. One is a Dark Spirit overhears Azula's call for power (if she survives), asking for the powers of the Avatar. This spirit gives her the knowledge to bind the??element to her body by force, going through the Avatar cycle in reverse (Fire, Earth, Water, Air), counter to the natural order. Whither it is binding elemental spirits or the bending powers of other, I don't know.

??Bascially, to me I see no 'new' bending styles coming up. I also see that the comet holds more than we know. But if that is a dark Avatar or something more powerful than the Avatar...

??Well, if you want to continue with the idea...

??The best that comes up is the idea of Marvel's Darkforce. In my Marvel Superheroes RPG Shadow Control power is different from Darkforce. Shadow control is a power over natural shadows using them to create darkness and shade as such. Darkforce is an extradimensional force that has a semi-sentiant nature that seems to have a hint of savageness or evil connected with it. But it also creates darkness and??shade, but also creates shapes of energy and teleportation plus flight powers.

??It could be possible that the Dark Avatar has harnessed the power of darkside of the Spirit Realm. A dark reflection of the bridge that the Regular Avatar is. This power increase the power of Bending, but has the effect of corrupting the soul of the use and tainting the element that is used is some way (for example Fire/Lightning bent in this was turns black, Water turns slimy and/or poisonous, Air turns Toxic, Etc). Plus the??fact that the Dark Avatar can easily give people the knowledge of the method of this bending style. Perhaps even??developing a method to??grant bending to non-benders.??Let's call it Darkbending as it brings out the darkside in people and is linked with the Dark Spirits of the Avatar world.

??::Note:: No Shadowbending is used, but the idea of a warped Bending style is still used.

??The Corrupted Bending can only be healed by special knowledge or links to the spirit realm that is not channeled by the Dark Spirits of the Spirit Realms. Elements bent by the Avatar or those who have crossed over to the Spirit Realms have the effect of neutralizing the corrupted element, but if not trained the results are explosive. The ability to use the Good Spirits to enhance bending is hard to learn and harder to master. Let's call it Spiritbending.

??Now this has a bonus effect of if a DA Arc is used for the next three season, if the creators want to continue with a seven or more season with Aang, the can use the Dark Spirits that granted the power to the Dark Avatar. Link back?? to his creation (perhaps both good and evil spirits were used to bind the spirit of the world to the Avatar and the evil spirits some how created a dark echo), the corruption of the Avatar Twin (offer of more power) or anything else.

??In this ideology Spirit bending would be represented by the Yin-yang sign as a path of harmony with the world. The Dark Bending symbol would be a similiar symbol but with a pure??Black Yin and a pure White Yang or a symbol with two pure white Yang (or two pure black Yin)??circling each other. This would represent the disharmony of Yin and Yang (Unbalanced Yin and Yang) that the bending would represent.

??Just my opinion.