I was thinking of mainly just roleplaying as life. And then the other celestials will be like 'NPCs' that we can also control. Maybe make a list as to who controls which celestial or a free for all kind of thing.
Maybe we should start simple with Death coming to earth to search for Life and as the story progresses, we'll add more characters. I think that Earth shouldn't be able to go to earth because Earth is ... well ... earth.
Now since Death can't risk doing what Life did (to make a mortal body) because they'd need as much power as they can use to maintain the process of killing off the humans, they will go to another celestial.
I don't know what the other celestials will be though ...
Maybe Time, Creation, Fate ... stuff like that?
Spoiler: For Time, Creation, and Fate's plan
Now that I typed that up ... maybe Life is in charge of creating new souls, Creation makes the mortal
containers bodies (animal and human) and Death cuts out the souls? Earth is in charge of being the planet and Time is in charge of deciding when a soul has to die. Fate takes the souls and redirects them to other surplus bodies that Creation makes.
Now as to why the other celestials will plot against the three ... maybe we could add in religion? Most humans praise Life, the rest Death. No one prays to Time and Creation thinking that it's the job of Life and Death. Fate hates being cursed or being used as an excuse by the humans.
Now these three, T, C, and F, want all the humans to pray to them or something ... forgot the term for that. If they take Life and Death out of the equation, they can use Earth as a playground for their plans (maybe not knowing that Earth was nearing its death). Fate can forcefully tear the souls from the bodies into the new ones that Creation makes. People will have to pray to these new gods that: A. They won't age (Time), B. They won't die (Fate), or C. They'll get a better body/self when they are reborn (Creation).
This should actually be beneficial to Earth since there is no increase in population, but without Death cutting out the souls and Fate tearing them out, maybe some of the souls would feel the pain and turn into vengeful spirits that destroy the earth? I dunno
So with Life being in earth for a hundred years, the amount of souls created was lessened giving Earth a breather. Earth asks Death to find Life for their answer. Death goes to Creation for a mortal body. Creation purposely makes a flawed body (Maybe. I don't know how the body will be flawed) and Death goes to earth to find Life. T,C, and F starts their plan by attacking Life and Death's realms little by little so the two celestials will not notice that they're slowly growing weaker ... maybe.
Ehehe, this was long
Also, shouldn't this be in the In-thread RPs section as well? o.o