Iden

"Only his body is over there. His spirit is floating in the air over here, and no, I don't know how it happened. Matoro thinks it has something to do with his mask. He says there are five Matoran not far away who are looking for us.""How does he know?""Um, well, he says he flew through the mountains ... straight through the rock, like it wasn't there ... and he saw them ... but they couldn't see or hear him."

- Toa Inika Hahli and Jaller, Power Play

The Kanohi Iden is the Mask of Spirit. It allows its user to temporarily release their spirit from their body. While released, their spirit can move at great speeds and inhabit other living (yet spiritless) bodies or self-powered robots. Their original body will become limp, though, as there is nothing inhabiting it. Only those who wear Kanohi Elda or Kanohi Rode can see and communicate to the user's released spirit.

While released, the user's spirit cannot access any of their body's powers, because the use of powers requires a union of the spirit and the body. Their body is also vulnerable, as they have no way to protect it themselves. If the user's body is killed, their spirit will eventually fade away, as they have no body to return to.

Multiple Kanohi Iden-users have the ability to swap bodies by sending their spirits into each other's spiritless bodies. A Toa's powers are tied to their spirit, however, not their body, so if a Kanohi Iden-using Toa goes into another body, the body will have the spirit's Elemental Powers.

Example Usage
Matoro used his Kanohi Iden to monitor Hahli's progress as she attempted to retrieve the Kanohi Ignika while underwater in Inferno.

Great

 * Toa Inika Matoro - Formerly; changed into his Kanohi Tryna when he became a Toa Mahri.
 * Toa Isxe/Toa Haru Kovek

Powerless

 * Kovek - Formerly; became Great when he transformed into a Toa Isxe.
 * Matoro - Formerly; became an organic Great when he transformed into a Toa Inika.

Trivia

 * The reason why BIONICLE author Greg Farshtey didn't want Matoro to have Elemental Powers in the story when he released his spirit is because it would give him an unfair advantage, since Matoro could attack beings who couldn't sense him.
 * If a Kanohi Iden-user goes into a corpse and a Kanohi Tryna-user focuses their power on the deceased body, the two mask-wielders can work together to imitate the deceased being.