Trantoshen

It is unknown when Trantoshen was created, but we know Trantoshen was created by Kakamu with a genetic manipulator at some point in his early life. Trantoshen left the Matoran Universe some time before Kakamu became a Makuta. When he heard that his father was dead, he vowed to destroy all Makuta. He somehow found his way into the realm of shadows and he got the Kanohi Daran and the Guardian Fire Spear.

Some time later, he discovered a Makuta named Klak. While trying to destroy him, Trantoshen was knocked to the floor by TMV-Spirit Nui. They fought.

Suddenly, the Fellowship of Kakamu appeared out of nowhere and kidnapped him, believing that they had found Kakamu.

When Kakamu was revived, he took over Trantoshen's body.

Because Kakamu was in Trantoshen's body when he teleported inside concrete, Trantoshen is technically trapped too.

Quotes
"Ynot once trapped my father inside a cage made of iron. I learnt a few things from my father, when he was alive. Now the Makuta must be destroyed so he can be avenged!"

--Trantoshen talking to TMV.