Yeah, I see that - I tinkered with how I wanted to put my thought on the subject. I could see it being Darkseid himself, but I read Mercury's line as referring to something different and not an escalation of the threat from Apokolips. Maybe I'm reading some of the Trinity War rumors into this. I was very impressed with what I saw as an in-joke: if you're going to replace the war against Nazi Germany as the crucible for the Earth-2 heroes, you might as well use "Steppenwolf" as the villain. It's the next best thing to using "Fancy Captain Nazi Pants." Also, Steppenwolf looked like Magog to me.