Before you ask questions:
 
“Who’s Mata–?” Mata-Nui, from Bionicle: The Legend Reborn. A movie that I fell in love with when I was a kid.  
“Why Celestia?” It was hard for me to choose who should be Mata-Nui. I first thought of Fluttershy, then Twilight, and then Applejack. I decided on Celestia because in the movie (Spoiler Alert), he was a ruler.  
“Why doesn’t Celestia have her mane flowing?” I shorten her height and loose the flowing because I wanted her to be more of a normal pony-like.  
“Why Bionicle?” I felt nostalgic.
 
Hope that’s answer your questions. Now on the description.
 
Here is my (terrible) job at making armor for Mata-Celestia. It was kinda hard turning Mata-Nui’s armor to look more on the Ponyverse. Since armor is a bit different in Equestria than it is here.  
I’m going to do another one soon.
 
Bionicle belongs to Lego  
Celestia belongs to Hasbro