Kaita

A Kaita is a fusion of three beings into one single being.

Toa Kaita
A Toa Kaita is a fusion of three Toa. Once the beings fuse, they turn into a completely different Toa with another personality, mask, and weapons.

Only two have been formed so far:
 * Akamai
 * Wairuha/Wairuha Nuva

Those two were the Toa Mata Kaita. Other Toa could form one, but just didn't. A Hordika can't form one since they lack the mental focus to stay together.

Matoran Kaita
A Matoran Kaita is formed when three Matoran fuse. As long as they have seperate elements, they can be formed.

None have appeared in the storyline, but two could be created from the McDonald's sets.

Turaga Kaita
A Turaga Kaita is a fused form of any Turaga of different elements. Unlike the other Kaita, a Turaga Kaita required four Turaga to form.

None have appeared in the storyline, but one could be made from the Vakama, Nokama, Matau, and Nuju sets.

Rahkshi Kaita
The Rahkshi Kaita were fusions of three different Rahkshi. Only two have appeared so far:
 * Kaita Za
 * Kaita Vo

Bohrok Kaita
A Bohrok Kaita was a combination of three Bohrok into one. Unlike most Bohrok, these had two Krana. None have appeared, but two are known to eixist:
 * Kaita Ja
 * Kaita Za

Bohrok-Kal forms of these two could be formed as well.

Bohrok Va Kaita
The Bohrok-Va Kaita are fusions of three Bohrok-Va into one larger being. None have appeared in the story, but two were combiner sets.