Toa of Shadow

"Something was nagging at him … something else that was not as it should be. What was it? He was certain that his armor had not been all black before … so that was one possibility. But was that the answer? No, no, it wasn’t. He was almost positive that one other thing had been different prior to his awakening.
 * ''He was pretty sure -- could have sworn, really -- that he hadn’t wanted to destroy the world before. But now?
 * ''The dark Takanuva just couldn’t wait to get started."

- Narration, Dwellers In Darkness

Toa of Shadow was a title given to Toa who had had all of their moral Light drained out of them, allowing them to wield the Element of Shadow. As Matoran of Shadow did not occur naturally in the Matoran Universe, a Toa of Shadow was impossible to create until the Makuta created Shadow Leeches. After that, Toa of Shadow could be created either by finding a Matoran destined to be transformed into a Toa, draining their moral light, and exposing them to Toa Power, or by finding an existing Toa and draining their light. Should a Toa of Shadow fulfill his or her destiny, they were given the option of sacrificing their Toa Power and becoming a Turaga of Shadow.

Powers
A Toa of Shadow's Elemental power gave them near-perfect command over darkness. As such, at a basic level, they could create, control, and absorb shadows. Examples of this included creating darkness, controlling shadows, and generating blasts of darkness. Toa of Shadow possessed all these abilities on a vastly greater level than a Turaga or Matoran of Shadow.

A Toa of Light posed a threat to Makuta and other Shadow-wielders, as they controlled light, while Toa of Shadow commanded darkness. However, Makuta and Toa of Shadow were a threat to them for that same reason.

Personality and Traits
As a Toa of Shadow was completely drained of moral light, they were purely corrupted and evil. The only way to reverse the moral corruption of a Toa of Shadow was to use a Klakk or finding someone to create the right sonic frequency to shatter the mental barrier blocking the return of the Toa's moral light.

A Toa of Shadow's armor color was a combination of black and whatever their primary elemental color was before their light was drained. Toa of Shadow could also be either male or female, as they could only occur artificially using existing Matoran and Toa.

Known Toa of Shadow
Below is a list of the known Toa of Shadow:
 * Takanuva - Main dimension; partially, later cured
 * A unknown number of Shadow Takanuvas - Alternate Universes; at least three deceased

Trivia

 * Ahkmou was at one point planned to be turned into a Toa of Shadow as part of the 2008 storyline, though these plans were later scrapped.