If you just need to rename all files in a folder this will do it, however it will only change the first letter, so demon skeleton.xml becomes Demon skeleton.xml. If you prefer Demon Skeleton.Xml, replace name.capitalize() with name.title(). Put the script in the monsters folder and run it, but be careful, because it will just rename every file in any subfolder of where you place the script. You need Python installed though.
Python:
import os
for root, dirs, files in os.walk('.'):
for name in files:
os.rename(os.path.join(root, name), os.path.join(root, name.capitalize()))
Otherwise
Requests is more suitable to ask for someone to make a script for you.