Secret Character/Playing With

Basic Trope: A character which can only be unlocked by a complicated means, often a Guide Dang It.

Straight: Prince Hi ro, La nce, Den nis, Mar cy, and Clau dia must take Olivia with them to unlock the Mon Persephone, otherwise Olivia dies.
Exaggerated: The steps to getting Persephone are: talk to two random NPCs, go to three certain areas, check an object too early, listen to a rumour, and take Olivia. As well as that, let some party members have a fight with someone, talk to another person who isn't so random, continue through the game, and wait for the event to be triggered. None of this is hinted at anywhere, making a massive Guide Dang It.
Justified: The events to getting Persephone lead in to her arrival.
Inverted: A monster which needs to be obtained, and can be done so quite easily, to advance the plot.
Averted: All monsters in the game are obtained easily.
Invoked: Breakout Mook Character