Via Lumpley [1]

My guideline was: in each oracle, enough stuff specific to that oracle (so like, enough ghosts in the Unquiet Past, enough soldiers in God-kings of War) plus enough normal stuff for the ghosts and soldiers to interact with. Otherwise the Unquiet Past is all ghosts interacting with one another, with no merchants' sons or whomever to get caught up in it.

Somewhere in that process I alphabetized the lot.

Once I had my four oracles, I just sorted them each into a random order and slapped cards on them down the line. So no, I did absolutely no planning about which elements got which cards.