Æons of Death is a massive compilation WAD that brings together monsters, weapons, and items from numerous games, such as Heretic, Hexen, Quake, Quake 2, Quake 3, Half-Life, Duke Nukem 3D, Blood, Shadow Warrior and others. ZDoom is required to play it.
The mod uses a randomization code which causes any monster or weapon in a certain class to spawn a random monster or weapon respectively. For example, in place of an imp, a snake imp, or a kilmaat, or a catharsi, or one of several others might appear. Also, in place of a shotgun, a shotgun from Doom 3 or the Arc of Death from Hexen might appear. This guarantees that it will never be the same game twice.
The old version (5.29.1) had implementation of classes. There were six class groups (Arcanum, Crawl, Cult, EDF, The Cabal, and UAC), with three characters in each group. Each group had an unique set of starting weapons as well as a unique HUD. The members of each class group vary in starting max HP, default movement speed, jump height, voice samples, and SFX.
6.02 includes many new weapons and monsters. It also introduces a difficult which causes monsters to spawn anywhere, where the player is not looking.
The latest version is 6.06.1, a major overhaul of the mod's mechanics including a new weapon, enemy, toggleable themes, extras, and directors.
This WAD was "awarded" Worst Wad at the 17th Annual Cacowards. 
Aeons of Death had different versions through the years. The first ever version released was 2.0 but the latest version is 6.02. Version 1 never existed or was never released to public. Below you will find the latest version available for each different version.
1. Version 2.4
This is the first and oldest version ever. There were mostly monsters from the Monster Resource WAD and a few from some popular FPS games. The only inventory item was a health bottle.
2. Version 3.01
This is the second version of AEOD. It was very similar to 2.4 but added new runes and removed some boring monsters, as well as fixing bugs. Before they released V4, they also released a Crawl patch which was a bit similar to 4 and 5 what became later.
3. Version 4.21
The third version of AEOD. It added a lot of stuff and fixed bugs, but was also the most unbalanced version out of there because there were very powerful monsters.
4. Version 5.29.1
The fourth version of AEOD. It had more new stuff such as, more weapons and the implementation of player classes. Other features added since version 4: Monsters that can transform you into chicken with 30 HP, and medical kits stored in inventory are auto-used to prevent death when low on health , etc.
5. Version 6.02
It removed classes, bestiary monsters but added new modes in which you can select the theme (example Doom theme).
6. Version 6.06.1
The latest version of AEoD. Removes the anti-cheat system, rebalances many aspects of the game, introduces one new weapon (Soul Reaper) and one new enemy (Weeping Angel).
Themes can now be individually toggled on and off, allowing for mixed-and-matched games of almost any type, unlike 6.02. Includes the ability to enable directors (monster and/or infected directors). Includes one game mode which overrides themes, and spawns nothing but the Infected from Left 4 Dead.