2007, the year of the Barraki, by far, my favorite year of Bionicle.

I grew up on these toys, since 2001 where the whole thing started, but I was really captivated by the story in 2007, where everything became dark and relatively sophisticated. 

This is Kalmah, the red Barraki. Essentially, the Barraki were warlords who were imprisoned in the Pit, a deep sea prison surrounded by mutagenic water, and when a quake released them from their cells, they were transformed into monsterous creatures that resembled sea rahi, and were unable to escape the pit as air was poisenous to them now. 

Kalmah, being the second smartest of the barraki, was my favorite, and had five tentacles sprouting from the back of his head that could detect incomming attacks from water movement, had three eyes (though only two work, his third eye was cut out by another barraki), and was armed with a large and powerful tentacle.