Strange Aeons

Strange Aeons is a 4-episode partial conversion for ZDoom/Ultimate Doom developed and released by Impie in the summer of 2015. It features 36 new maps and a large number of new weapons, powerups, and monsters. Many elements of the wad are based on the works of horror author H. P. Lovecraft, in particular "The Dream Quest of Unknown Kadath," and as a result the megawad is very atmosphere-heavy.

Releases
Strange Aeons was planned as a four-episode megawad for ZDoom, with the main story concluding in Episode 3. On July 22, 2015 it was released as a 3-episode beta. Episode 4 was added a month or so later, and the mod is currently still in beta.

Story
The player controls the nameless Traveler, a Miskatonic University researcher who has recently lost his son David in a tragic accident. To cope with his loss, the Traveler has begun an obsessive translation of the Kadath Tablets, which appear to have a strong connection to the treacherous Dreamlands. After seeing visions of his son alive and well in a utopian world, the Traveler embarks on a dream quest, traveling across the cosmos through his dreams in the hope of reuniting with his son.

Episodes
Each of the three episodes takes place in a unique world that is drastically different from the others. The Shattered City has a "broken world" motif, with buildings and rock formations drifting through empty space. The Stagnant Fortress features rusted, dilapidated buildings of the future filled with toxic sludge, crushers, and conveyor belts. The Land That Time Forgot is a prehistoric world with a vaguely Egyptian/Aztec theme. Occasionally these worlds bleed into one-another, such as during the boss battle at the end of World 1, where the Traveler is suddenly transported to World 3. The bonus episode, Plateau of Leng, takes place in an icy, mountainous wasteland populated by gunmen and giant spiders, and serves as the story's epilogue.

Weapons and Powerups
Strange Aeons modifies a couple of the original Doom weapons, and replaces most of the weapon sounds.
 * The pistol has new graphics and sounds, but behaves the same.
 * The most notable change is the AK47, which replaces the chaingun and fires slightly faster.
 * The plasma gun is replaced by the Yithian Lightning Gun, a powerful weapon which can only be found on the secret levels.
 * The 'Scepter of Souls is added to the arsenal, behaving like a mid-range chainsaw that requires no ammo.

In addition, three new powerup artifacts are present.
 * Ammo Sphere gives the Traveler unlimited ammo for a short time.
 * Rage Sphere doubles the firing rate of all weapons.
 * Mutant Sphere turns the Traveler into a towering hulk that smashes monsters with his fists, but cannot pick up items.

Assets
The entire bestiary has been replaced with modified creatures from Realm 667, many modified to resemble creatures from Lovecraft's Cthulhu and Dream Cycle mythoses. Custom graphics were made for the Episode 2 and 3 end bosses. The vast majority of the level textures are from Chasm: The Rift, as is the majority of the soundtrack and many of the sound effects.

Lovecraft Mythos
In addition to references to Dream Quest of Unknown Kadath and the inclusion of the Plateau of Leng, the mod has a number of other Lovecraftian elements. - The hooded shotgunners are referred to as the Men from Leng, and are among the most common enemies. They move and shoot twice as fast as a normal Doom shotgunner. - Modified dianogas called Spawn of Glaaki attack the player in watery areas. The dianoga has a striking resemblance to Ramsey Campbell's one-eyed, slug-like deity. - The player frequently makes use of ghoul allies in Episode 2, which eventually leads to the Underworld and a massive final battle on the Vale of Pnath, a fortress on top of a mountain of human skulls. - The boss of Episode 2 is the massive Dhole, many of which dwell in the Vale of Pnath. The preceding battle between ghouls and demons awakens several of the beasts and draws them to the player. - Spider god Atlach-Nacha serves as the final boss of Episode 3, and the primary antagonist of the main plotline. This is why its worshipers, the Leng Spiders, are commonly seen throughout the mod as enemies, symbols, and otherwise. - Nyarlathotep appears more than once as a "bonus" boss who must be avoided rather than fought. - The Star Vampire is infrequently encountered throughout Episodes 3 and 4. It is essentially a flying Nightmare whose laughter gives away its presence. - Flesh Spawn are referred to as children of the vile deity Abhoth. - The mod's ultimate weapon is the Yithian Lightning Gun, which is powerful enough to tip the balance of the game considerably. It is hidden on each of the four secret levels.

Other notes

 * Impie based the project on the first "Doom clone" he came up with following his first exposure to Doom in 1995.
 * The partial conversion comes with a pdf "instruction manual" which describes the story, new additions, and asset authors.