First Time Dming, need tips about my campaing

Sorry for my bad english

My campaign will be focused around the gods and monsters in 2e, kinda like a castlevaniana/the witcher vibes.

Basically monster and such will appear a lot more in goraidon, the barriers who separate the planes will turn weaker and weaker, that happens because Lamashtu, urgathoa and zen-kuthon would unite to do what they want with the world, while pharasma, serenrae and iomedae would try to stop that. Asmodeus will kinda play both sides, just wanting to manipulate the party and get a profit.

The players will probably join one side and fight the minions of the other, while going into their own character development, later they would discover that the one who started this god war and Broke the "plane-barriers" is Nyarlathotep.

Them the party would try to separate the planes again, probably using some artifact, (or try destroing it to mantain separate forever).

Nyarlathotep will be doing all that just to have fun, so by great sacrifice and a really hard fight with him, he can leave goraidon or fullfill a wish to the party, or some bullshit like that.

I also planed some "possible paths" to my friends character, just to prepare myself and make hooks for their development