Kaita

Kaita were fusions of three beings into one single being.

Toa Kaita
Toa Kaita were a fusion of three Toa. Once the beings fused, they merged into a completely different being with a distinct personality, Kanohi, and weapons. Only two Toa Kaita have been seen thus far: Akamai and Wairuha, formed from the Toa Mata. Other Toa could form Kaita, but didn't. Toa Hordika couldn't form Kaita, as they lacked the mental focus to stay together.

Matoran Kaita
Matoran Kaita were formed when three Matoran fuse. As long as they have separate Elements, they could be formed.

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

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

None 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 exist:
 * Kaita Ja
 * Kaita Za

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

Bohrok-Kal Kaita
Three of the Bohrok-Kal could also merge to form a Bohrok-Kal Kaita. Only one has appeared in storyline, though two are known to exist:
 * Kal Kaita Ja
 * Kal Kaita Za