It is supposedly the Hand of Creation (no references), but I suspect it is the hand of Krona, having gone back in time to witness the Big Bang, in some perverse way actually causes or assists the event by observing it. In any event, his witnessing the birth of the universe (there was technology involved) caused the creation of the Anti-Matter universe and the multiverse as well.
Krona was an arrogant scientist of Malthus (the species to later be known as the Oans) who desired all the secrets of the Universe including its origins. In his arrogance, he alters the nature of the universe and creates instead a Multiverse.
Krona has the most complicated origin story ever especially since it has been used to explain the creation of:
Out of Universe
The Big Bang in the DC Universe has been the source of contention, a multiversal dumping ground where villains too big to deal with are often sent, or strange storylines are created (See: Time Trapper).
The Multiverse was a construct of the previous Pre-Crisis universe where multiple active timelines interacted. This was a construct of the DC Universe having several companies which formed from the purchase of different comic companies over the years. Golden Age Superheroes were relegated to Earth 2, while more modern versions or Silver Age heroes became the heroes of Earth 1. This feature of the DC Universe became popularized in the famous tale, The Flash of Two Earths.
The Multiverse was temporarily made into a single construct during the Post-Crisis stories, while DC tried to meld all of its previous properties into one cohesive universe with a single timeline. Heroes were eliminated and different versions of characters were either worked into history or eliminated. This fix was later repealed with the Zero Hour crisis and has now been replaced into the New 52 universe where 52 distinct timelines have become the new multiverse. DC will, once again, separate its divergent worlds and use them for alternative storylines. (See: new Justice Society of America)
Krona: Crazed Malthusian with a lust for knowledge so great he fractured the space-time continuum.