Changing actors involved in events and recruit locations

If you wanted to add a character during a boss fight, that is slightly more complicated.

All of the properties of the character need to be set up before they're used in battle (numbers 1-8 in the list PowerPanda listed), and you need to rewrite the battle event, add the characters to the party during the fight (you'll have to look at battle event scripts), and again add the character to the party afterwards (number 9).