Been looking back over all the stuff revolving around this.... Not sure I'll mention anything that hasn't been said already, but here's my two cents for what it's worth.
Death's whole job is to make sure people die. But not just that they do, but that they do in the right way at the right time, yeah? He's neutral in all this Apocalypse stuff, he's bloody Switzerland, just there to keep things rolling as they should. So, obviously, he was pretty pissed off at the people that have cheated him cause that messes up his whole point of existance. World can't keep going without death, it's the whole cycle of life and all that. He's obviously real anti-Lucifer and his Apocalypse...I beg to say that if Lucifer wins, there's likely to be a load more immortals around, so that wouldn't help. World doesn't have it's natural cycle if Lucifer wins, either.
This prize bit is what gets me. I've seen someone viewed that way before. The one seeking it gets real single-minded. Won't let anything get in the way, anyone that tries to stop 'em meets their maker. Thing is, there's always a loophole somewhere. Doesn't mean it'd be a good one. Becomes very much a situation of choosing the lesser of two evils, which is hardly ever an easy thing to do because no matter what, you lose somehow either way... Said he's not at our beck and call, only gonna be around when we need him. I've got a feeling whatever it was that as supposed to be done to talk to him didn't work, and probably isn't going to.
And what about this "fulfill your purpose" bit? There's got to be more to it than just...don't cheat Death. People are pulled into this damn place for a reason. Maybe we should work on trying to figure that out.
And now I feel like I'm just repeating everything that's been said. Bloody hell I hate this cryptic shit.