Infected Kanohi

"It is through these masks that Makuta controls the Rahi."

- Gali, BIONICLE Chronicles 1: Tale of the Toa

Infected Kanohi were any Kanohi (Great, Noble or powerless) that had been infected by a Kraata or a Makuta's power. They appeared rusted and old, and whoever wore one was under the control of the Makuta who infected it. Although a Makuta could infect Kanohi directly, they usually let Kraata do it instead. If the infected mask was removed, the wearer would be temporarily stunned and the Makuta would lose control over them.

History
Makuta Teridax infected many Rahi during the 1000-year period before the coming of the Toa Mata, and used these animals to keep the Matoran on Mata Nui from returning to Metru Nui. On Mata Nui, the Matoran sometimes called the infection 'the Madness'.

After the Toa Mata arrived, they succeeded in freeing most of the Rahi from Teridax's power. Later, when Teridax personally faced the Toa Mata in the form of a Matoran, he altered the Kraahkan's appearance so that it appeared as an infected Hau.

Shortly after Teridax released the Rahkshi onto Mata Nui, a Shadow Kraata infected at least two Matoran. These Matoran were later freed from their masks.

Example Usage
In the Mata Nui Online Game, Lewa's Great Miru was knocked off and replaced with an infected one, forcing him to serve Teridax. The Kanohi was later removed by Onua.

Great

 * Toa Mata Lewa - Formerly; mask since removed.
 * Teridax (in his Matoran form) - Actually the Kraahkan

Powerless

 * Some Mata Nui Matoran - Formerly; all masks since removed/uninfected.
 * Various species of Rahi - Formerly; all masks since removed/uninfected.

Trivia

 * An infected Hau was often used to represent Teridax.
 * Shadow Kraata could infect Kanohi over distances, unlike other types of Kraata.
 * In the Dark Mirror alternate timeline, Teridax wore a Great Hau that appeared infected.