Alexis Luthor (Michael Rosenbaum) has figured it out...

Alexis Luthor: ..".. ah.. ahh.. Society Lex.. I figured out where we .. were.. we were in the fourth dream realm.. in the dark matter dream realm.. in the heavy, black matter dream realm... in the Giganta dream realm, the fourth dream realm of the year 1929... I always felt that Giganta would call herself composed of the quintessence and substance of dark matter, of heavy matter, of dense matter, denser matter.. just like Superman's denser cells are Giganta's denser, heavy matter, dark matter cells... Giganta feels herself very much composed of the substance and texture of .. black matter.. black matter.. black matter.."...