In the LEGO BIONICLE universe, masks, or 'Kanohi', play a significant role. Each mask provides its wearer, often a Toa or other significant character, with specific powers. Over the course of the BIONICLE theme's lifespan, several masks were released as exclusive or promotional items. These exclusive masks became highly sought-after by collectors.
The BIONICLE theme is series of sets based on modified TECHNIC pieces and ball-and-socket joints to create larger figures. Bionicles coincided with a series of comic books and graphic novels released during the set's run from 2001 to 2016. The theme was introduced in 2001 and originally discontinued in 2010, being succeeded by Hero Factory but additional sets were also released up until 2016 after it's break in 2010 to 2014. BIONICLE sets were tied together by an elaborate original storyline within the comic books and other multimedia that centered around bio-mechanical characters which are generally large, powerful beings that usually serve for good. The name BIONICLE is short for BIOlogical ChroNICLE.