So the god of the dead raises an army of the undead (zombies) and meanwhile a alien race of advanced robots attack earth...

I wish I could respond with something that sounded more awesome than what you just proposed, but I cant. All I can add is that the players would have to survive a zombie invasion that could drive them mad, or risk being captured by the robots and enslaved as a partial cyborg, whilst what remains of their human bodies now has an insatiable lust for brains.

How bout that cyborg zombies, using robotic enhancements to make them faster, stronger and all the more deadlier.

How about this (going off your idea)

Aliens invade and start turning the dead into mindless zombie cyborgs to increase their ranks, some maybe getting enhancements (to explain whatever variants). The god of the dead takes offense to this as he's only allowed to raise the dead and proceeds to raise his own army to fight the aliens. The other gods get involved trying to stop all this. We are simply caught in the middle.

How about this (going off your idea)

Aliens invade and start turning the dead into mindless zombie cyborgs to increase their ranks, some maybe getting enhancements (to explain whatever variants). The god of the dead takes offense to this as he's only allowed to raise the dead and proceeds to raise his own army to fight the aliens. The other gods get involved trying to stop all this. We are simply caught in the middle.

Jeez I hope they manage to fit the cross compatibility into this line like they did the Star Wars stuff.

Or else, well it probably won't be pretty.

Cross play would be awesome. Since it's going to be a staggered release I could see something like this occur:

Zombie Apocalypse

humans start attacking other humans but in a more primal way, biting, scratching and people start hearing about dead bodies getting up and walking around attacking those nearby.

Wrath of the Gods

It is revealed that the god of the dead has been slowly amassing an army for his war on the other gods and the war officially takes front and center.

Alien Invasion

Aliens invade in the middle of it all and realize their folly and begin to build robots to fight their war.

Revolt of the machines

These robots begin to become self aware and start improving themselves and the aliens lose complete control over them.

The aliens eventually leave and the gods retreat back and the robots begin farming human bodies for their resources and start "growing us" trapping our minds in a virtual reality.

I definitely don't want them to be part of the same universe. The possibility of cross-play is fine in my book, but a never ending apocalypse of ever rising risk just takes away from each component.

that would be a pretty crazy scenario but it would allow your campaign to evolve as the books are released. Keeping things fresh especially on long term campaigns.

My players are excited by the possibility of this. I can't wait to find out more about the system in general and when I can give them my money to buy this.

Even if they didn't include specific rules I think they could be used interchangeably if one wished to do so .

aliens vs zombies, vs machines vs gods...

And mankind sitting on the sidelines watching the whole thing and eating popcorn