How do I change a unit?

Got it! Thanks! But how do I do what I need then? Or can I create normal links to files?

Added 4 minutes later
This error also broke the game itself, specifically the affected units.
The only way to fix this is to delete this map-mod. Of course, it's also my fault; I remember encountering something similar when I was experimenting with Assassins. You need to save such maps after changes using "Save As" so that you can "roll back" if something goes wrong. Otherwise, it's a dead end. It's an unpleasant situation right now.

In theory, you just need to copy the Banshee files and then the Undead file, which contains all the information, and then split it into separate lines and insert these lines into the Banshee files.
And also make the links to the Undead files similar to the Banshee files.

In short, split the single Undead file into files like the Banshee files. But I haven't done this myself; it should work if everything is inserted correctly. It's just a different way of presenting the information to the game. Not in one file, but in parts... materials separately, skeleton separately, geometry separately