Search the marvelmods forums, the bone structure for MUA was described in several different places. You rip the models to edit them with DX Ripper or any other similar software that can "steal" models loaded into system memory, edit them with your 3d editor of choice, then export them with...

You might want to visit marvelmods.com, which is a site devoted almost entirely to modding this series of games. For clarification, IGB files are Alchemy engine (which is what these games use) model/animation files, but the animations and models are stored separately =) XXX_charactername.igb are ani...