Project Einherjar is a five-episode total conversion for GZDoom/Doom II developed and released by Mike MacDee (Impie) in the summer of 2016; Episode 2 was later released in the winter of 2016; and Episodes 3 through 5 throughout early 2017. It is set during nuclear winter, and features 35 new maps and a totally replaced roster of weapons and enemies in the style of an early-90s 3D shooter. Impie made the mod as a promotional gimmick for a dystopian novel series set in the same universe. The gameplay involves lots of fast, brutal shootouts with enemies that die relatively easily, but can badly injure the careless player. Each episode features a short story that sets the stage for the action to follow, written in the novel's pulpy style.
The mod series is referred to as "Winter Agent Juno." Impie got the mod series title from a Japanese review blog's description of the mod: "Winter Agent Jin: Destroy the Armored Sisters Institute!".
Impie later released a fan mod of the Wolfendoom episode Operation: Arctic Wolf using Project Einherjar assets.
The player takes control of the novel's protagonist, Juno, in the postnuclear nation of Midgard, which stores its male population like cattle in "Valhalla" facilities. Under direct orders from the government, Juno has begrudgingly rounded up all known homosexual males in her Valhalla and delivered them personally to Gaulheim, to be experimented on by the homophobic Dr. Gaul. Juno is about to leave when a runaway male explains that Gaul is turning the men into mindless super-soldiers as part of a coup to take over the government. Juno reports this to her superior in the capital city, but Dr. Gaul is too well connected to move against officially. Instead, Juno is given permission to discreetly liquidate Dr. Gaul and her super-soldier program, Project Einherjar, while a blizzard cuts Gaulheim off from the rest of civilization.
The subsequent episodes involve new villains reviving Dr. Gaul's Einherjar project in various forms, forcing Juno into conflict with them.
Project Einherjar completely replaces the player's arsenal.
- Martial Arts - Juno has two deadly kick moves when this weapon is selected. As of version 5.3 and up, the secondary kick attack is always available no matter what weapon is selected.
- Ballistic Knife - Juno's signature weapon, a knife that fires the blade like a small harpoon that pierces all enemies in its path. The blade must be retrieved after each shot (if it isn't lost forever due to poor aim), but she can collect extra blades during the episode.
- Raven M40 - A fast-firing and highly damaging pistol.
- Shit Creek Scattergun - A slow shotgun Juno constructed from water pipes and other junk. A last-ditch resort for getting a better gun.
- Thunderhammer Auto-Shotgun - A fully automatic version of the shotgun.
- Gungnir M14 - A fast, deadly, and accurate assault rifle. It can usually hit its mark at long distances even on full-auto.
- Dessler Frag Cannon - Pump-action rocket launcher. It fires more slowly than the Doom 'Launcher, to balance the squishy and mostly human enemy roster.
- Mako Gauss Cannon. A type of rail gun that pierces enemies like the ballistic knife. It does much less damage, but can be fired rapidly; however, it requires precise aim to deliver a killshot and is only recommended for expert players.
- Silenced Raven - A Raven M40 variant that trades stopping power for silent shots that don't alert enemies. Only found in secret areas.
- Spring Mine - A landmine that bounces into the air before detonating. Juno is immune to its destructive effects.
- Missile Pod - Once dropped, it fires off four salvos of mini-missiles that seek the nearest target.
- Super Stim - Heals Juno like a stimpack and grants her temporary 3/4 damage reduction for a few seconds. It also negates the effects of morphine darts for as long as it's active.
One distinguishing feature of the mod is that each enemy type has a unique personality to distinguish it from the rest of the cast. It can almost be summarized as a gender-swapped Wolfenstein 3D; the boss characters even have large, distorted anatomy much like the bosses of Wolf3D and Spear of Destiny.
- Title screen: Tyrian - Title Theme
- Intermission: Code Veronica - Escape Theme
- Text screen: The Terminator: Rampage - Floor 1 Theme
- Endgame: I Am Jimmy by jmickle66666666
- It is one of the few Doom wads that makes heavy use of a snowy environment and a mostly female cast; it is also possibly the only Doom wad where homosexuality is a central plot point.
- Players are encouraged to use jumping and crouching to reach extra items and take advantage of cover during firefights.
- The TC comes with a pdf "instruction manual" that details the story, items, and characters. The mod's plot is a spin-off story that is not directly connected to the plot of the novel, with the exception of a reference to how Juno lost her eye, her use of a ballistic knife, and her ability to improvise weapons on the go.
- Many of the locations, names, and weapons are taken directly from the novel's universe, especially the use of Norse mythology (Fenris, Einherjar, Valhalla, etc).