Throughout the vast, 3.5 year lifespan of the TBTTRAH series, there have been multiple main characters. Here's a list of some of them.
The Tahus
The Tahus, or Tahu & Tahu as they prefer to be called, are the co-leaders of the House and the Bionicles living inside of it. The group consists of a Tahu Mata set and a Tahu Nuva set, both of which have been with the group of Bionicles since they first managed to come to life. Tahu is a hot headed, but fiercely loyal, leader who is very devoted to leading the Bionicles correctly. He has a strong disliking for Pridak, the rest of the Barraki, and really any other trouble makers at the house. Tahu is also a Boston sports fan for some reason, and has been known to hit people with baseball bats just for being Yankee fans.
Tahu Nuva, on the other hand, is a patient and levelheaded co-leader that usually gets Tahu out of the trouble that Tahu gets the duo into. Tahu Nuva has an obsession for windows, however, and goes beserk when a window is smashed. Tahu Nuva, due to his calmer nature, has never been anywhere near as many crazy situations as Tahu, and thus has not suffered from any signs of insanity.
Pridak
Pridak is the leader of the Barraki and is the biggest troublemaker at the house. He is constantly trying some new creation or making some new plan, which usually ends up with someone getting hurt. The "someone" is not limited to other people, however, as he once attempted to kill Mesonak with a knife and ended up getting his right arm sliced off. A quick surgery by Toa Zehvor Brenmac managed to save his arm, however.
Pridak has a strong hatred for Mesonak because of this incident, and is currently planning some sort of revenge. He also happens to dislike Tahu because of his strict-ness(though it was Tahu's quick thinking that saved his arm), and dislikes 4 Mask as well for kidnapping him. Pridak's best "friend" is Zaktan, and he is usually able to talk Zaktan into getting the Piraka to join the Barraki for Pridak's plans that involve more than 6 people.