Hello there, Isaac community!

I'm making a small mod that lets Delirium transform into the alt path bosses. I have some sprites ready in the correct folder, but they don't seem to be showing up in game. Delirium can transform into the bosses, but they display the standard sprites instead of the unique ones that I made.

Does Delirium require some code to know what sprites to change into? I have zero coding experience, so that would be unfortunate to learn. Thanks in advance!