Exo-Toa were armored suits capable of enhancing the powers of those who wore them. They featured advanced equipment including electro-rockets.
When a Toa donned the Exo-Toa armor, he wielded more power than any being on Mata Nui had ever known. The Exo-Toa were hidden underground for centuries. The Exo-Toa featured a mighty claw arm and an awesome electro-rocket.
An Exo-Toa hindered the elemental powers of the Toa who wore it. It also required tremendous strain to use mask powers such as that of the Mask of Shielding while in an Exo-Toa.
Exo-Toa had an electro-rocket on one arm. When worn, the wearer could feel power seeping into his or her body. The Exo-Toa inhibited a Toa's elemental powers.
Exo-Toa could also act on their own, without an occupant. They were no match for the Bohrok-Kal.
When wearing the Exo-Toa, Tahu was referred to as Exo-Tahu.
Those who created the Exo-Toa put them near the Bahrag's chamber as a failsafe to be used to stop the Bahrag if the Bohrok were ever released too early. The Bahrag never removed them because they never saw them as hostile, since the Bahrag were doing what they were doing when they were supposed to.
Exo-Toa were not built for the Toa Hagah. They were designed to function independently on the orders of the Brotherhood of Makuta.
Exo-Toa were not designed to be used independently. They were designed to guard Brotherhood of Makuta fortresses and were likely piloted by Toa even if Teridax's Hagah didn't use them.
The Exo-Toa were not designed to be bodyguards for the Brotherhood of Makuta; the Brotherhood reprogrammed them.
The Exo-Toa were designed by Matoran.
The Brotherhood of Makuta were the original creators of the Exo-Toa.
Exo-Toa were not very intelligent. They essentially just destroyed targets they saw.
Exo-Toa intelligence was probably A.I.