The Bahrag are characters from the Bionicle storyline of 2002 and 2003. They are the Queens of the Bohrok swarms in Bionicle. They resemble twin dragons, with only different colors (Red and Blue). They create the Krana that drive the Bohrok, apparently by dipping stones in a pool of an undefined substance (most likely Energized Protodermis), and drawing Krana from it, according to BA#6: Maze of Shadows.

Cahdok and Gahdok have all the Bohrok powers, as well as telekenisis, telekinetic energy shielding, and illusion projection. Also, they become stronger when they are closer together. The Bahrag released The Bohrok-Kal to steal the Toa Nuva's symbols and free them from their Protodermis prison (See Toa Nuva).

There was once a third, yellow, Bahrag - named Tahdok - who was deafeated by Towhunga (Mctoran/non - rebuilt Matoran) prior to the coming of the Toa. Remember - the Turaga knew nothing of the Bahrag, and could only indentify it as one of the beasts in the picture (in BA#6)
Coincidently, the whole Bohrok and Bahrag events have a similar concept to the Quranic story of Yajuj and Majuj and their swarms, which live in a cave that will one day break out and swarm the Earth.