Andros Melos has speculated that Guar was originally a being who decided to split himself into the three siblings.
With all of the Guar Army members killed except them, the three leaders of the Guar Army decided to merge into Guar to finally defeat the Andros Warriors.
Guar initially had the advantage in the fight against the Andros Warriors, as its amoeba physiology made it nearly impossible for the Andros Warriors to damage it with attacks. However, the tide turned when Andros Melos used the Grantechtor to destroy Guar at the cost of its destruction.
Having trouble dealing with Xio's defenses, Mold Spectre called forth his siblings souls and fused them into himself to create Guar Spectre. He was combated by Ultraman X, Ultraman Ginga and Ultraman Victory. However, despite their teamwork, they proved unable to stop the beast.
Ginga and Victory then combined into Ultraman Ginga Victory while Ultraman X transformed into Exceed X. Guar was ultimately defeated by a combo of X's X-Lugger Shot and Ginga Victory's Zepellion Ray and left unable to revive due to X purging the Dark Thunder Energy from its body.