You can play the normal Entaku no Seito game anyhow you like with any party you want and beat the final boss just fine. If you want to succeed in the post-game, however, there are a few things you’re better off having, some of which will need preparation several hours in advance. This post (the last on Entaku no Seito, I promise) is to warn you of such things so you can get your affairs in order and not be forced to grind like crazy for something you would have gotten easily if only you’d known.
The most important spell for postgame is Levitate, and the most important thing for postgame bosses is Union Skills + Levels, so the earlier you finalize your party, the better. For the record I went with MC, Lumi, Chupp, [post-game character], Eltha and Lolon. I haven’t actually beaten the bonus boss yet, but his doom is assured, hence this post. [update: beat him, see way down below] Do please go on, this is most interesting



