I think it would require a trilogy to involve Darkseid in Doomsday's arrival on Earth so the easiest explanation I can think of is Doomsday being born from the rock Superman took into space at the end of Returns. His blood + the crystals + the kryptonite x crashing to Earth = Superman Dead. As I suggested in my Justice League thread on the Superman Returns Sequels board http://www.superherohype.com/forums/showthread.php?t=249330 I think the following picture is how Doomsday should be realized. I'd imagine him as an elemental character-- like Sandman and Swamp Thing. I think the following picture also gets at what I would want from Doomsday: The next picture was a concept for Burton's Doomsday. Thank god that never happened.