There are some characters who join your party in an RPG and they are only there for a little while, or don't follow you forever. In order to bring them with you to the final battle, you may have to do a sidequest or hack them.
Perhaps the most famous one is Aerith but no need to really give her any tribute, cept she had good limit breaks. (Which I didn't know about)
One of the greatest examples would be Final Fantasy II and IV. Both of them, IV moreso, had a revolving door of characters with a lot of them being temporary. Some were pretty useful, like Yang and Tellah (Until Palam and Porom catch up that is) and some were useless...like Edward until the DS Remake and hard version. (Does Salve work with Elixirs? He vanished from the party before I had the chance to obtain any)
Jeanne d'Arc also has a temporary character.
Spoiler Below Liane is in your party for a good majority of the game before she is burned at the stake due to Jeanne having been removed from the party...yeah, weird that the MAIN CHARACTER was actually absent for several hours' worth of the story, huh? Well Liane's death is also a pretty big plotpoint for the game, since that's when Roger goes crazy and the Reapers start to show up, and it still affects them throughout the rest of the game, especially the battle with the Reaper that was fused with Roger...even if she was nothin more than a Decoy while Jeanne, Richard, and Gilles de Rais did all the work.
But said character is replaced with someone who has the same stat growth. Probably because said temporary character was my healer and you're forced to use them a lot.
What temporary characters did you like?