Not my own words, but: "Enjoy memes and have a good time online, but develop a solid sense of self-worth that is rooted in a reality that doesn't disappear when the battery charge is empty."
Since the setting isn't Legend of Zelda, there ought to be more to their history than a carbon-copy of themselves in that universe, shouldn't it? How do they fit into the roleplay's setting and what have they been doing for the last century?
I have a bad habit where I'll start a book, then move on to other interests and leave it halfway for a month or more. Then I'll eventually come back to it little by little and charge through the ending.
I'm currently grinding through Brandon Sanderson's Way of Kings and I have the rest of the Stormlight Archives on standby. But I've been hitting the Del Rey Conan anthologies as well!
One problem I foresee is with the massive number of people, there are different expectations for the RP, and its 'fantasy' setting in particular. One person's idea of fantasy might not necessarily jive with another's, and if the RP starts without a clearly-defined tone, it can mess things up later on.
So folks will be playing nations/peoples that arose from the fall of old empires, left to their own fates, trying to make sense of the ancient world they left behind?
Could be cool - are you leaving it up to the players to create a cohesive history, or do you have something in mind to work from?