Download "Vanilla Doom Plus" -monster randomizer (UPDATED AUGUST 12TH) 
  Hello,   This is a mod I originally made for myself. I was desperately looking for a monster randomizer like this, and I couldn't find one. So I started editing "DoomKrakken's Monster Randomizer"... and really liked what it started to shape into. So I decided to start from scratch. So that I can also share this with everyone, in case there's anyone else out there also looking for a mod like this.   The name "Vanilla Doom Plus" might be a little misleading. To me "vanilla doom" just means doom without any extra mods. Playing vanilla style(no jumping etc.), but still using a source port. I use GZDOOM and it's the only source port I have tested this mod with. Works with Doom, Ultimate Doom, Doom 2 and Final Doom. And should work with any mod that only adds maps.   My goal was to make a monster randomizer that only adds monsters. And still would be well balanced, if you're playing maps that have been designed for vanilla gameplay. I've mainly been testing with Ultimate Doom and Doom II.   Every monster that replaces a certain enemy has the same(or smaller) radius and height settings, so they shouldn't get stuck anywhere. Every monster has a specific set of monsters that can replace them. When killed, every monster that replaces shotgunguy will either drop a shotgun or shotgun shells... Same idea with chaingunners and zombieman. This is to maintain ammo balance closer to the original.   I also wanted that each "group" of monsters wouldn't infight other monsters from the same group. For example the monsters that replace imps wouldn't infight with each other at all. I didn't know how I could have done that at first. Thanks to user Tango for pointing me to the right direction on how to do it!! It was an easy fix and works very well now. Some enemies do have attacks that can still cause infighting, but I think it's rare enough. And also monsters that replace monsters that normally would infight with each other(like zombies and lost souls) are untouched.   BY DEFAULT SETTINGS: This is a more "subtle" monster randomizer. You'll see a lot of regular monsters(over 50%). It's very much Doom, but there's a lot more variety. There is about 220 added monsters. Some of them just are very rare. More common monsters like imps and zombieman have a higher chance to be just regular versions of themselves.   There is a "REPLACER SETTINGS" menu with A LOT of options for Spawn chances etc. Thanks to whatup876 for suggesting for me to do these option menus!   Some power-ups have about 1 out of 30 chance to be replaced by another one. For example SoulSphere can be replaced with LifeSphere which gives you 300 health.
And some decoration objects can be replaced by stationary monsters and mimics.
These are very rare, and those can be turned ON/OFF from the options menu.   I also have changed a lot of properties of the monsters... Health, painchance, attacks etc. For example if something replaces Baron of Hell. I want it to have ABOUT the same amount of health. And if something is replaced by an enemy that could kill you a lot faster than the original monster. They probably have less health than the monster they replaced. But these are not very common.       VIDEOS(using earlier versions of this mod):
SCREENSHOTS:     This is FAR from perfect. That was never the goal. I just had a lot of fun making this. I originally stopped working on this about 8 months ago. This week I decided to do couple minor tweaks to it, and finally share it. EDIT: I have done a lot of changes since the release!   I made this the way I liked it. Obviously thanks to every cool monster made by various people!!   I hope you'll have fun with it too!   ALL THE CREDIT GOES TO: ID Software (obviously) Raven Software Everyone who have worked on any of these monsters. Realm667 DoomKrakken and DoomKrakken's Monster Randomizer. I used it a lot to see how these things are done in Slade. And huge thanks to Doomworld users: Tango, Bryan T and whatup876!! For helping me to fix couple issues with the mod. And great suggestions.