Doom 25th Anniversary, OR FREEDOOM PHASE 1, YOU NEED EITHER DOOM 2, FINAL DOOM, OR FREEDOOM PHASE 2. And also remember to set Doom 2 as the IWAD and the Starter Pack as a pwad (I have seen people hosting this as iwad and loading doom 2 over it as pwad. It's just nonsense and causes bugs) If you see lots of missing textures being replaced by white textures with green squares it's because you are loading a wrong
How do I set up the files?
This mod actually has stolen and plagiarized assets. DON'T EVER support a mod that has asset theft.
How to run?
You don't. This mod has stolen assets anyway. Better off reporting this fraud mod than setting it up.