Black Might Gaine is a near identical copy of Might Gaine, formed from the combination of Black Gaine, Black Might Wing, Black Locomorizer and Black Pilder (not necessary).
Black Might Gaine himself is a homage to Mazinger Z, in his debut pose. The black color scheme and having the Black Pilder docked on his head, are the direct references to Z.
As the same for Black Gaine, Black Might Gaine is an exact copy of Might Gaine based on the stolen data, with only a few differences such as a brand new color scheme, chest sigil, and head cover, along with a new fourth component to the combination known as the Black Pilder, which docks on top of Black Might Gaine's head.
During Episode 16, Hoi Kow Lou ordered the combination of Black Might Gaine to fight against Might Gaine. After a long, tough battle, Might Gaine emerged the victor with his Tate-Ichimonjigiri technique, delivering a damaging but non-fatal slash. After the skirmish, Black returned to his former self, with Black Gaine soon detaching, taking the control mask with him in order to prevent Might Gaine from being hijacked, and eventually exploding himself mid-air. His head fell in front of Might Gaine, and shared his last words with him before shutting down.
However, it seems that Black Gaine's A.I was still intact and functional, as he was seen being rebuilt alongside the other Brave robots in the final epilogue.