The Underworld is a text based forced transformation game for mature audiences including erotic content such as: furry, monstergirl, male to female (MtF) transformation, oviposition, lactation, and more. Along the way, you’ll meet a wide cast of characters across the three factions that each have their own ideology about how to deal with people different from themselves. Your actions will determine which faction achieves victory, and by extension, the fate of humans and hybrids alike.
Latest Update: r37 - Chapter 7: Aquatic Aquarium Released (Private Build)
Infiltrate the Mulberry Aquarium and become one of the anthro/monstergirl exhibits! Transform into a horny mermaid, a fat whale, and a powerful shark. All the while the other creatures in the aquarium seduce you in front of a rapt audience of tourists and visitors. Will you accomplish your mission and escape the aquarium... or just become one of the lusty wildlife?
The largest chapter update ever in Underworld history! Full post here.
Fan Art Corner
Dragon Queen (ch3) fan art by Ghostbun
Dinoian (ch6) fan art by HAPPYFACES
r36 - Mermaid TF & Water (Private Build)
Become a lusty, buxom mermaid in r36! That heavy mermaid tail will keep you stuck in the water, and being a horny merslut, lust attacks will hit you for double damage. But unlike humans, you can breathe underwater. Currently, you'll be stuck in a test pool with the octomaid, but she knows just how to keep you company with those tentacles ;)
Full post here.
r35 - Wyvern Male & LUA Powered Monsters (Private Build)
Encounter the Wyvern Male, a monster who is eager to turn you into his breeding mate. He'll take good care of you, ensuring you're knocked up with eggs and milking your four large tits when they grow too heavy. The wyvern is quite a dominant partner, and will remind you of your place... and thanks to your new breeder instincts, you'll find yourself becoming quite submissive to him and his dual cocks. He has about 7k words of content (roughly the entire length of Chapter 2!) for a fun variety of scenes.
Modders also gain a range of new tools, including the ability to create LUA powered monsters and entity-to-entity communication.
Full post here.
r34 - In-Game Mod Browser / Mod Portal (Private Build)
You can now easily browse and install mods -- all from right from inside the game! Full post here.
r33 - Female Breeding Wyvern TF (Private Build)
Become a female breeding wyvern in the newly released r33 build! Fight against (or give into :3) your new mating instincts as you become a horny quadruped with a huge, egg-filled belly.
Full release notes here.
r32 - Chapter 7 Intro (Private Build)
You finally make contact with the shadowy Baosheng Group and discover Krista is becoming a cowgirl. Will you return her to human, send her to the farm, or keep her for yourself? These three different endings will greatly affect the future of VCiV.
Also includes proper tracking, display, and save/load for the Faction Point system.
Full release announcement here.
r31 - Teasing Tentacles (Private Build)
- Shark TF - Become a powerful anthro shark!
- Tease system allows NPCs to tease you based on your new body.
- Octomaid, a half-octopus sea monster who knows just where to put those tentacles of hers...
Full blog post here, including some more details on the tease system.
r30.03 - New public demo build
A new public demo build is now available! Since the last demo build, this includes:
- Tattoos & Piercings system - Get one to force yourself to always be lusty, or prevent your breasts from ever decreasing in size. You could even get one to get rid of those pesky attack options so you have to always submit to your opponents...
- Choose initial acceptance level - There are now three options during character creation to decide your initial acceptance rate and how you treat others. Each option has its own little intro story to go with it, along with an explanation of the acceptance system.
- Better organization of inventory UI.
- More reliable keyboard shortcuts.
- Numerous other small improvements and fixes.
r30.01 - More Modding Support / Wolf TF (Private Build)
r30 is released, including new transformation features for modders. A Wolf TF sample mod is available to demo the new quadrupedal/paw support for modded transformations. Also, don't forget to check out the Dragon Queen enemy mods by Saint!
r29 - Permanent Tattoos (Private Build)
r29 adds support for Permanent Tattoos that make you more obedient, lusty, or cause other effects.
r28 - Piercings (Private Build)
This update features a piercings system for wearable piercings that cause various effects to your character.
Want to force yourself to always be lusty, or prevent your breasts from ever decreasing in size? Or wear one to get rid of those pesky attack options so you have to submit to your opponents...
r27 - Choose Initial Reaction (Private Build)
There are now three options during character creation to decide your initial acceptance rate. Each option has its own story to go with it, along with an explanation of the acceptance system. One of the options even lets you TF Becky some more ;)
r26 - Map Mods / Spider Dungeon (Private Build)
Can you steal the treasure from the spider nest and escape? Or will the spiders get the best of you and transform you into their mate, forever filling you with brood after brood of spider eggs...
The new Spider Dungeon map demonstrates the new support for Map Mods, allowing you to create your own maps to explore in the game.
r25.01 Dinoian Fixes (Private Build)
The Underworld r25.01 is now released - I accidentally broke the Dinoian chapter in the previous release, so if you had trouble with that, please grab the new build. Also includes some other misc dinoian chapter text fixes & save fixes.
r25 Modding Requests (Private Build)
r25 adds a number of features requested by modders. You can also check out our first user-created transformation (Pig TF by Luxious) if you like weight gain stuff, including both a Pig King enemy to fight and a cursed transformation pendant.
r24 Transformation Mods (Private Build)
You can now mod your own transformations into the game, including the first transformation mod: Anthro Giraffe TF. The r24 build also includes a new auto-login system which will be especially useful for Android players, along with an update to the game's business model. Additional details on the blog.
r23 Mod Support for Items + Clothes (Private Build)
r23 is now released to all private backers and includes the ability to mod in your own items and clothes into the game! These can be simple text-only mods, or can be driven through LUA code. There’s a number of new sample mods available, including the cursed weight gain pendant which will cause you to gain weight continuously.
r22 (Public + Private Builds)
The main new content for public build players in r22 is Frog TF:
Now the frogs in the swamp chapter can now transform you into one, too.
4000+ words of chapter 2 content including different scenes when the Naga Queen defeats you based on what form you’re in. The minions are a bit smarter too, and won’t try to transform you if you’re already a frog or slug (unless you’re not 100% in that form, in which case they’ll try to re-transform you if you’re of the matching species). Frogs and slugs also now leave a slime trail wherever they go, which can re-transform you if you use it (it’ll eventually evaporate). If you track slime into Nixie’s shack during the swamp quest, she’ll comment on you making a mess of her place.
Frog form is another in the all-fours category, since frogs can’t stand upright. As frogs naturally gain weight over time to get that nice frog belly, that can eventually cause their movement to be difficult. At larger belly (and optionally breast) sizes, it will drag on the ground beneath them and sometimes get stuck in the slime as they travel. If you go farther and intentionally max out belly/breast sizes... good luck moving at all.
Additional New/Updated Functionality:
- UI Updates / DPI-aware layout
- Wait Button
- Entity Selector
- Retuned Dragon Queen oviposition rules
- Added reduce cream to hospital shop, and as an item occasionally dropped by foxgirls.
- Misc text fixes
r21 (Private Build)
Chapter six: "Dinoian Desert" is finally complete and ready to play! r21 is available for download for all full game / private build backers at the researcher intranet in both SWF (PC) and APK (Android) flavors.
This build includes the release of the Dino Chapter.
At the conclusion of chapter five, you incapacitated Thornton by transforming him into a catgirl, leaving him trapped to work in Mulberry's strip club while you steal his identity. You're now able to sneak into his convoy, which will allow you to cross the vast underground desert to scout out SkyCorp's research laboratories for the rival faction, VCiV.
What should have been an easy ride across the desert turns out to be much more than you bargained for. The convoy rides on specialized creatures that are genetically engineered to withstand the tough conditions of the desert. These dinoians could best be described as a distant anthropomorphic cousin of a velociraptor, or perhaps some sort of wingless riding dragon. One of them, Hanako, is planning her prison break, and you haplessly stumble into her plans.
Soon she's stealing your identity. She forces you to wear her old leather bindings, transforming you into a dinoian that looks just like she used to. She had unintentionally acquired the reputation of convoy slut, and now that you have her identity, she intends to make sure you live up to her old behaviors so as to not be suspicious. Every time you disobey her, she increases the size of your cleavage, making you hornier as you're forced to expose your nearly-naked body to the world as she rides you. To make matters worse, thanks to your monstrously large dinoian vagina, you won't derive any joy from copulating with humans -- so your body will work against you to force yourself to mate with your fellow beasts. But they're in a similar predicament, former humans trapped in lusty bodies that have no choice but to serve their riders and their base desires.
Try as you might, dinoians are forbidden from speaking thanks to their vocal cords which can only make animalistic noises. Though you desperately want to explain your situation, no one can understand you. Even removing the bindings themselves is impossible as they self-replicate to ensure you can never be freed. Stick around long enough, you'll start to enjoy serving your rider. You may even begin to enjoy being tied up with your wrists bound, further restricting your opportunities for escaping this life.
Will you succumb to your dinoian need to be filled up and lay clutch after clutch of eggs? Or will you find a way to escape your fate and complete the mission?
Backstory is revealed about the history of The Underworld, along with the factions that vie for power inside it. Three endings, one for each faction, are available -- each with their own puzzles to complete. Can you find all three?
Clocking in at a massive 30,000 words, this chapter is nearly three times as long any that has come before!
Finally, I'd like to say thank you for everyone's kind words and encouragement during this massive chapter's development, whether that be in blog comments, discord, or wherever. I've never tried writing anything this huge before, and I couldn't have pulled it off without you cheering me on. So thank you, and I hope this chapter brings you much enjoyment.
Past update summary
- r5 [public] - UI improvements, including the popularly requested customizable font size [details]
- r6 [private] - Weight TF system - Eat food to replenish HP, but if you over-eat you will gain weight which will make your belly difficult to conceal [details]
- r7 [private] - Panda TFs - Transform into a panda [details]
- r8 [private] - Cowgirl TF - Transform into a cowgirl, lactate, at high levels grow an udder [details]
- r9 [private] - Chapter 4: Cowgirl Farm - The next story chapter, which includes forced TF into cowgirl [details]
- r10 [private] - Shop system [details]
- r11 [public] - Bug fix & public build [details]
- r12 [private] - Added Elephant TF, Cat TF, and multi-breast TF (five new transformation items total). [details]
- r13 [private] - Chapter 5: The Pound (Catgirl Stripclub TF) [details]
- r14 [private] - Horse TF (horsedick / autofellatio), Tiger TF (multibreast), Turkey TF (inflation) [details]
- r15 [public] - Public release of: Horse TF, Tiger TF, Turkey TF, multibreast items. Also adds portable milker. [details]
- r16 [private] - Mobile / Touch support & APK build [details]
- r17 [private] - Female Spider TF (egg laying) [details]
- r18 [private] - Monster Mods, Male Spider, Custom Name Entry [details]
- r19 [private] - Save support [details]
- r20 [public] - Public release of: Cloud Save/Load, Custom Name Entry, Mobile/APK Support [details]
- r21 [private] - Chapter 6: Dinoian Desert, Frog TF, UI Updates, Wait Button [details]
- r22 [public] - Public release of Frog TF
.// Welcome to SkyCorp Employee Mainframe //--
MOTD has been updated by root in the past seven days
Attention! All SkyCorp employees are to be alerted of outbreak of VIR-819 in Mulberry and surrounding areas. Original infection of virus into human populace traced to -REDACTED-.
Progressive exposure of the virus causes mutagenic effects in human subjects. Infected are highly contagious, causing additional mutagentic effects on humans they contact. So far, documented mutagenic effects have included: hybrid fox transformation, hybrid dragon transformation, increased libido, gender changes, and oviposition. Due to the chaotic nature of VIR-819 and the denizens of the Underworld, the infected are likely to encounter all prior mutagenic effects listed. Additional mutagenic effects are expected as the virus evolves.
SkyCorp has lobbied and received regional government funding to build the Underworld, an underground complex where infected creatures are mandatorily required to relocate to upon discovery. Investigative journalists have indicated this network contains at least one shantytown, a sewer dungeon, some sort of mysterious temple, and various connecting passageways. However, SkyCorp personnel must strictly occupy only the town of Mulberry and other overworld areas for their own safety, unless they have received designated security training. Additional areas are expected to be found as exploration of the network continues in future.
Employees should encourage Mulberry citizens to be ever vigilant of signs of infection. Infected creatures have been known to mask their mutations with clothing and feign humanity -- but these creatures are dangerous and must not be allowed to run free due to their changed nature. SkyCorp has identified at least one suspected sympathizer in town who has been providing aid.
Employees interested in researching The Underworld/VIR-819 are requested to download the training materials.
A recent copy of Adobe Flash will be required (Flash 11+), and employees are requested to file a summary report on their experience in Mulberry and surrounding areas. Prospective trainees are advised as to the early and experimental nature of this program.