Doomtale is a crossover AU of Undertale and Doom. This AU has the tone of Underfell.
Long ago, two races ruled the Earth: Humans and Demons. One day, war broke out between the two races. After a long battle, the victorious humans sealed the demons in a hellish dimension. It can only be broken with a power equivalent to 7 human SOULs.
Many years later, 2106... Horrific beasts have been sited across the globe. People believe that the demons have come back for revenge. So, they sent a 30 man group of highly trained marines in order to find out what was going on. Mere hours after they were sent into Hell, their communications went offline. The humans' signals went dead and it was assumed that the humans were as well.
Eventually, it was decided that one man would find out what happened. People were confused, saying "How will one man solve our demon problem if we couldn't do it with 30?!" The superiors stated that this man has faced worse odds before and always came out on top. They described him as "too determined to die." This man was then sent to begin his mission.
The monsters are replaced with monsters/demons from the Doom franchise. The monsters here are genuinely trying to kill you like in Underfell. And just like in Underfell, King Asgore enlisted a "kill or be killed" policy. Because it is similar to Doom, the Genocide Route might come as instinctive. The Pacifist Route is entirely possible, yet it is VERY difficult to do.
To be added
True Pacifist Route
To be added
The Genocide Route might come as instinctive to Doom players. There are some differences. Toriel, Papyrus, Mettaton NEO, and Asgore will all put up a fight in the Genocide Route. You can spare Papyrus at any point in his Genocide fight and immediately end the battle. Sans has 300 HP instead of only 1. He also has 78 Attack and 98 Defense, making his fight much harder. He still has Karmic Retribution.
After you kill Asgore in the Genocide Route, Zane the Z-Sec shoots you in the head with a shotgun, takes your SOUL and radio and crosses the Barrier himself. Despite not having a SOUL you can use the last of your power to perform a Reset.
If you do a Genocide Route a third time, Sans will fight you at the end of Snowdin and, if you kill him, triggers a Disbelief timeline. Disbelief Papyrus will attack you in the Judgement Hall with Cacodemon Blasters, bones, and rockets and will block all of your attacks with a large bone. Eventually, you can break that bone, making Papyrus truly angry. He will not stop attacking if you are down to 1 HP. Eventually he uses one final attack that is unavoidable. He restricts the bullet board to make sure the Protagonist's SOUL cannot move. He then summons a large Cacodemon Blaster over said SOUL. He will then move it over the FIGHT button and blasts that instead, effectively making the Protagonist unable to fight anymore and the Genocide Route unable to be completed. All you can do at this point is ACT, ITEM, and MERCY.
Flowey the Flower is now a Z-Sec (Zombie Security) named Zane. He is a Machinegunner class. He wants to get out of hell as much as you do. He will teach you how the fight mechanism works and tell the protagonist that "In this world, it's kill or BE killed!" and that "mercy" is not in the demons' vocabulary. The Protagonist then asks how Zane knows what it means. Zane says that he was a human once. He will act as a companion, fighting by your side. He will say you're wasting everyone's time if you are sparing the demons.
Napstablook is a Ghost (Heretic). He can't die. He will leave if the Protagonist and/or Zane reduce his health to 0. He attacks with an Ethereal Crossbow. The arrows are glowing green. Unlike in Doom, Napstablook can only fire one arrow at a time.
Toriel is now a beige Hell Knight from the original Doom game. She more closely resembles a beige, stronger version of Fell!Toriel. She does not want you to leave the Ruins, as she fears that others will instantly kill the Protagonist. Her fight will begin at the door to the Ruins like in Undertale. Her fight is hard and sparing her is very difficult to do. She attacks with green fireballs. These do not heal you at all. She will not stop attacking if you are at 2 health. She will stop fighting you if you spare her 30 times. After the 35th spare, she will allow the protagonist to leave the Ruins.
Sans the Skeleton is a short, somewhat lazy Revenant. He has rocket launchers on his shoulders and blue body armor. He will hide the protagonist behind a conveniently-shaped stalagmite. He'll tell Zane that his brother won't pay much attention to him as there are plenty of Z-Secs roaming through Hell. He deeply cares for his brother Papyrus. Sans's No-Mercy fight will occur if you are on the Genocide Route, or have killed Papyrus and more than 20 monsters. Sans will say, "remember 'kill or BE killed'? you killed wrong people. Dirty brother killer. but hey, don't worry 'bout it. you're 'bout to have... a REALLY good time." His Gaster Blasters are replaced with Cacodemon skeletons. He, like Papyrus, also fights with broken/cracked bones and rockets. He also has psychokinesis.
Papyrus is a tall Revenant with body armor, gloves, boots, rocket launchers on his shoulders, and a red cape. He wishes to capture a human to join the ranks of the Royal Guard. He still cares for his brother Sans and is still annoyed by his laziness and puns. He attacks with cracked or broken bones and rockets. He still has a Blue Attack. His Special Attack is a multitude of Cacodemon skeletons that blast the Protagonist. However, a Hellhound takes the attack, forcing Papyrus to use "A REALLY COOL REGULAR ATTACK." After the attack, you have the option to either spare or kill him. If you spare him, you get to hang out with Papyrus.
Monster Kid is an ICE from Hacx. They idolize Undyne and wish to see her in action. They are an NPC, meaning you can't fight them.
Jerry, known as Joachim Rumohr, is a Wolfenstein Schutzstaffel trooper in a blue uniform. He wields a submachine gun. He gives no EXP on kill, meaning you can kill him and still do the True Pacifist Route.
The Mad Dummy is now known as the Mad Summoner. He is a wrathful Summoner who can't die. The only attacks that can hurt him are those from the monsters he summons. After enough turns of being hit with "friendly" fire, he resorts swiping at you and Zane. Soon, Napstablook shoots the Mad Summoner with Ethereal Arrows, causing him to leave.
Undyne is a Heavy Weapon woman. She is in a suit of bullet-resistant titanium armor. She also has a bionic eye that can shoot lasers. She still has a spear, but also uses weapons like chainguns, shotguns and a Hellshot. Her fight is similar to Undyne the Undying's. If you haven't killed any monsters (excluding Jerry) nor Papyrus, you can befriend her.
On the Genocide Run, she doesn't turn into Undyne the Undying, instead she uses a BFG 9K which she was able to get for 20K Gold. The weight of the Gold broke the shopkeeper's table.
The Temmies are replaced with Imps. They reside in the Imp Village. There you can buy the BFG 9K for 9999G. However, you can negotiate it down to 7500G. You can't get this item in the Genocide Run.
Alphys looks largely the same. She also wants you to get out of Hell and is willing to help you along your way like in Undertale. She tells the Protagonist and Zane that she created a smaller Inquisitor called "Mettaton". She says she did this because "Inquisitors are as big as two tanks stacked on top of each other. Plus, Reavers aren't that bright."
Mettaton is a human-sized Inquisitor with a human-like face. He has the Protagonist do seemingly random things like he would in Undertale. He is still a famous celebrity.
Muffet is a bipedal Trite. She runs a bake sale like in normal Undertale and is very expensive. She will attack the Protagonist if they haven't bought anything. She will immediately stop fighting if you have purchased something from the Spider Bake Sale in the Ruins. She will not attack the Protagonist at all if they bought something from her bake sale.
Asgore is a Baron of Hell. He is still the king of monsters. He wants you dead and destroys the Mercy button. This forces you to fight him. After he is reduced to very low health, you have the option to either kill or spare Asgore. If you kill him, he will have a smile on his face. If you spare him, he says that sparing him will do absolutely nothing beneficial and performs suicide. No matter which option you choose you and Zane get to leave Hell.
On the True Pacifist Route, Zane absorbs the human SOULs and all Monster SOULs. After that, he becomes a Cyberdemon and then the Spider Mastermind from Doom 2016. It is your job to restore the memories of your friends and eventually Asriel himself. After you beat him, he will revert back to Zane but will remove his helmet, revealing the head of a Hell Knight from the original Doom. He will then break the barrier. Asriel Zane Dreemurr, as he will then go by will come with you to the surface. Surprisingly, the humans will accept coexistence with the Demons.
Frisk is the Doomguy or the protagonist of the Doom games. He always wears his helmet on, so no one can see his face. He wields a variety of weapons, but starts out with a pistol. He can pick up better weapons along his travels. Frisk only takes his helmet off after defeating the Spider Mastermind form of Zane. From then on, he keeps his helmet off, as he is done with fighting.
Glyde is a Maledict from Doom 3. He is rude and arrogant like in Undertale. He is a secret boss.
W. D. Gaster
W. D. Gaster is a Revenant in oddly pristine white armor. He has cracks on his skull and holes in his hand. He writes in Wingdings 1.
The River Person is now Charon the ferryman. He will charge 1 G for a trip to Snowdin, Waterfall or Hotland.
The Ruins are the Catacombs from Strife.
Snowdin is the Guardian of Ice map from Hexen.
Waterfall is the Confluence from Heretic.
Hotland is relatively the same.
Alphys's Lab is the Advanced Research Complex from Doom 2016
The CORE is the Reactor from Doom RPG.
New Home is a combination of the Necropolis and Argent D'Nur both from Doom 2016.
The True Lab is the Lazarus Labs from Doom 2016.
- You are able to kill Jerry because his Nazi beliefs would make him a threat to everyone including himself on the surface and Toby Fox confirmed that Jerry was the only character in Undertale that wasn't good.
- Doom!Sans's pre-fight dialogue was taken from a fan demo of Underfell.
- Out of the 30 humans that entered Hell, only 6 human SOULs survived, meaning that the other 24 SOULs vanished upon death like a Monster's would. Asgore had Alphys conduct experiments to find out what made these 6 SOULs so special.
- Doom!Undyne has fought Infected and won by default, meaning he ran away.