Mystic brothers comprises of Ostrich runner and egg header, the egg header splits into 2 to form 2 headers.
Mystic Brothers combination
Combining with the Mystic Brothers, Gosei Great becomes Mystic Gosei Great.
The Mystic Runner attaches to Gosei Great's left shoulder and the two halves of the Egg Headder attach to its feet, forming a shoulder-mounted flail.
The Mystic brothers set is more like a weapon attachment set then recreating a new mecha. This is combination is lacking but still has some nice playabilty.