Can someone explain DC's Apokolips to me?

Actually, Apokolips/New Genesis are in another dimension from Earth, unlike say Rann, Krypton, and Thanagar. Apparently, if you somehow go there without being translated through a Boom Tube, you’ll be really tiny when you come out. Supergirl found this out when she used her flaming wings* to teleport there in pursuit of some Female Furies.

*'Twas an odd period for the Maid of Might.

Neron is, though.

Just a quick question…are Apokolips and New Genesis somehow vital to the existance of the universe in some magical/cosmic sense—kind of like if you killed Marvel’s Galactus, the universe would end, or something—or could you get away with destroying one or both of them with a Planet-Killer?

They’re not particularly vital - a couple Elseworlds and potential futures have posited the destruction of one or the other. Apokalips was (accidentally) wiped out in The Nail, for instance.

“There came a time when the old gods died! The brave died with the cunning! The noble perished, locked in battle with unleashed evil! It was the last day for them! An ancient era was passing in a fiery holocaust!” - the opening words of New Gods # 1

Also, I’m pretty sure Apokolips is just a planet in our universe, but I can’t find my dc universe atlas to verify.

A little hijack: could someone explain how this works in conjunction with Hellblazer?

Are Lucifer, Azrael and Beelzebub of Sandman the same as the First, Second and Third in Hellblazer? If so, how could Lucifer both abdicate in Sandman and be killed by Ellie in Hellblazer, at which time he is very much still in control of Hell? How come Azrael can both be imprisoned in a glass jar by Dream and destroyed by the First? If they’re not the same, why doesn’t the First mention Lucifer when he’s telling his life story to Constantine in Rake at the Gates of Hell, and where are the Three during Dream’s visit to Hell?

[spoiler]The First of the Fallen predated Lucifer and his wave of fallen angels. He ruled Hell - or what would become Hell - before Lucifer arived, and he took the throne again after he abdicated. Nor are the Second and Third Azazel and Beelzebub. I have only skimmed Rake at Hell’s Gate (I’m still in the middle of Delano’s run), so I can’t say anything about his explaining things to Constantine, but the First does mention Lucifer when he’s explaining to the Second and Third how they’re not the same as him. Lucifer was either more powerful, or more clever and it took him clearing out for the First to get a chance to come to power again.

As to where they were in Sandman… They weren’t in power, they weren’t directly serving anyone in power, they didn’t hold any of Dream’s friends or possessions, they didn’t watch the gates and they either left Hell of their own free will or were driven off by Lucifer before Dream showed up for his tour of Hell. Dream, Cain, etc just didn’t run into them.

The only problem I’m seeing is what happened to Remiel and Dumas? Are they playing hands off? Does the First draw his authority from them? Did he manage to overpower them?[/spoiler]