I've discovered a bug where after beating the game and returning to the world, Izana will be invisible to the game, her overworld sprites and her "speaking" image are both invisible, her battle image remains visible. Her overworld sprite is actually viable when you first return, but is "ignored" by the warp effect, and upon a save reload, becomes fully invisible. Sorry if this isn't the best place to talk about bugs, couldn't find anywhere else other than steam.
As a side note, I thought the game was fantastic, one of my favorite tf games and just a very neat game in general, especially the essence and charm system . I would love to try and mod new forms and stuff for it, if the files are set up in any way to even allow for that and if that wouldn't go against your wishes. Art would be done by myself so there would be no worries there.