The mod changes most of the graphics from Doom II , as well as the weapons and enemies. It has new enemies and weapons for ZDoom , increasing the gameplay. It also brings some new enemies for Doomsday Engine. It doesn't use Legacy features, being only Legacy compatible. The story is a sequel to the New World mod series made by the author on 2004.
The player again takes the role of the same Doom marine from the original series. It's revealed that after the Earth invasion on Doom II and The Plutonia Experiment couple of years ago, he still works as a soldier. After his return from the newly discovered planet, he receives a message from his commanders about a small invasion occurring on some Earth industries. Being an experienced marine, he is called to finish the invasion.
The Marine goes to the Landing Base, the first of a series of six different industrial bases. These bases contained mostly human zombies and weak demons. After cleaning most of the bases, he reaches a Slime Machine at the Toxin Supplier. There, he receives a message from Command saying that the invasion has spread through out the capital cities - leading to full-scale invasion on Earth. The Marine is ordered to finish the industries and join the remaining soldiers on their effort to stop the invason. Escaping from the industrial area through a damaged dam, and cleaning some industry outposts, the Marine reaches the city's outskirts.
However, when he arrive, all marines were already dead and the fate of Earth is again on his hands. Cleaning much of the citie's areas, the Marine encounters a vacation house, where he decides that would be his home after the invasion. He then proceeds to the city's municipal park, where he finds a strange underground link between the park and the ancient Egyptian-like Temple of Waterfall. There, the Marine discovers the main gateway between Hell and Earth. As the Marine enters the portal, he receives his last transmission from Command. They ordered him to stop the invasion on Hell, since their job now is to rebuild Earth.
The portal, however, didn't lead him to Hell, but to a desolate ice place on Earth. After the Marine finds a small outpost on this land, he finds out that the portal can be manipulated through small panels, which changes the portal's destination. On Hell, the Marine manipulates the portal on different locations of Hell, until he reaches a great demonic canyon. There, he fights the Mega Vixen - a powerful woman demon which controlled part of the Hell's army. After her death, the Marine reaches the center of the invasion. There, he encounters another Icon of Sin - a different one, not brainless like the others, controlling Hell portals. After entering into the Icon of Sin's body and destroying his heart, the Marine finally stop the invasion and returns to Earth.
The mod ends with the Marine on an isolated beach house, with a unnamed naked woman. After thinking about the horrors from the war, he decides to stay away from politicians, war and violence and dedicade his life on pursue of peace and true love.
The project had three years of working, and the final product were much more different than it's initial version. In these three years, a lot of people joined the project, but in the end no one did a considerable quantity of work. The most notable feature of the mod is that it was the first multi-port megawad mod with Doomsday, Doom Legacy, GZDoom, Skulltag and ZDoom support. And it also can run also in source ports that have DeHackEd support.
The mod has a load of new weapons. Some are for GZDoom and ZDoom only, including the inventory items which are plentiful and are occasionally dropped by monsters, giving a sort of RPG feel to it. The new monsters vary from monsters from the Monster Resource Wad to original incarnations of bosses, including enemies from Hexen and Duke Nukem 3D. Some different monsters can be encountered depending on whether the wad is played with Doomsday or GZDoom/ZDoom. The ZDoom addons were made on the last year, only a few were kept on the mod, and the other weapons were releases as a weapon mod called "Arsenal".
The mod tries to bring some levels with new atmospheres for the Doom engine. Only a few textures come from the original Doom II, and the textures are divided into sets, very organized by the mapper. The two secrets levels also has a special theme: the first one being based on the author's house and the second one based on the "author's infancy". All maps have new textures or modified old ones. Another notable feature is the soundtrack: all music was made by Daniel himself, since he is a musician. The first levels have Techno-like music, the cities have hard rock tracks and the latest levels have atmospheric music that reflects the tension made by the hellish style of the maps. There also musics designed especially for a level, such as the second secret level.
The levels follows the standard Doom II mission storyline, divided up into episode-like sections, defined by their corresponding sky texture and separated by a textual intermission in addition to the intermission screen. It's important to note that first part of the industrial levels takes places on several maps not connected with each other, and after second part of the industrail levels, most of the maps are connected with each other.
MAP01 to MAP06, industrial tech bases levels
Level 1: Landing Base
Level 2: Poison Refinery
Level 3: Command Central
Level 4: Creature Prison
Level 5: Computer Station
Level 6: Toxin Supplier
MAP07 to MAP11, escape from the industrial bases and city's outskirts levels
Level 7: Slime Machine
Level 8: Damaged Dam
Level 9: Hidden Industry
Level 10: Sewerage
Level 11: The Mansion
MAP12 to MAP17, invested cities levels
Level 12: South Zone
Level 13: Residential Ward
Level 14: Center District (the original NeoDoom demo's level)
Level 15: Commercial Downtown (exit to secret level)
Level 16: Doom Shopping
Level 17: Municipal Park
MAP18 to MAP20, egyptian like temples levels
Level 18: Forgotten Fortress
Level 19: Temple of Waterfall
Level 20: Inner Temple
MAP21 to MAP29, Hell's levels
Level 21: Frozen Lands (takes places between Earth and Hell)
Level 22: Demonic Island
Level 23: Profane Cathedral
Level 24: Tower of Sufferin'
Level 25: Eternity Cemetery
Level 26: Underground Castle
Level 27: Demonic Throat Canyon
Level 28: Gateway To The Evil
Level 29: At The Heart Of It All
MAP30, the finale level
Level 30: The Return
MAP31 and MAP32, secret levels
Level 31: Vacation House (exit to secret level)
Level 32: A Brick On The Wall
NeoDoom had mixed to good reviews from players since its release. Many enjoyed the WAD for its level variety and originality, its powerful weapons and tough creatures. It was one of the most played WADs on cooperative on Skulltag.
Other players criticized its maps as being too "standard", and the amount of weapons and items making it too cumbersome. Players also complained about some of the monsters, mainly the Vixens, being way overpowered. The main controversy, however, were to the "stolen" material - which the author replied that it was unfounded, since all authors are credited on the text file. Another controversy was around the Cacoward at the 2006 ceremony, which the mod didn't receive. Apart from this, the WAD is arguably considered one of the most important Doom mods of 2006.