I voted for the plot,... but really, the best part about Zeal Kingdom is the endless threads of theory and speculation that can be built from its unknown details and mysterious past. Who discovered/harnessed magic? How were the Floating Islands brought to be? What happened to Schala and Janus's fathers (yes, fathers; there's a Zealean who'll tell you that Janus and Schala are step-siblings)? How long did the kingdom exist before its zenith and immediate demise? Was the Prophet originally part of Zeal's history when he was growing up as Janus (predestination/event loop theory) or did Magus knowingly risk changing the flow of events (as he seems to indicate in one of the alternate endings). And above and beyond all else... what's with the blue hair??
Yeah, Zeal is a treasure trove for conspiracy theories and unwritten backstories, as proven by all the Zeal-related fanfics out there.