This is a mod based on AlysiumX's Ultimate Invasion DM, adapted to not replace the monsters and instead their DoomEd numbers only, so now it should work with most gameplay mods (Except OMG Weapons and Monsters for some reason).
To play, bind the open invasion menu key to setup your preferences. There you choose your options, make sure to read them all!
Once you finish a wave many more enemies will appear on the next one, so be prepared!
Spoiler: ScreenshottyScreenshots can't really make justice to this (It would just look like I slapped a bunch of monsters in a deathmatch map) so I recommend you download it and try it yourself
Remember, type "InvasionMenu" in the console or bind the keys i set at the key configuration menu to set up everything on this mod.