The Milligan Shade is the same character as the Ditko Shade.
In Seven Soldiers, we learn that Darkseid can use the Omega Effect to place people in a "life trap," sending them through a series of increasingly grim incarnations of themselves. Clearly, when Darkseid used his Omega Beams on Shade in Suicide Squad, he inflicted this fate on Rac Shade. (Given the relative popularity of the Ditko and Milligan versions of Shade, this may qualify as a Poison Oak Epileptic Tree.) The Madness Zone is the same as Delirium's realm.
That's why Shade exhibits such Reality Warper powers.
