Viewing Mod
The Binding of Undertale
TBOI x Undertale Crossover Mod
Created 2 years ago

Get the AB+ version here:

Thank you very, very much for the Mod's overwhelming reception and 50000+ Downloads!

This mod replaces characters, music, bosses and floors with Undertale content! Enjoy!

by tipo19 and Opscat

Talk to us!

Q: Do I need Afterbirth for this to work?
A: No. Inside the folder, you can see there is a "Rebirth only" folder.

Q: Where's Toriel, Asgore and Chara?
A: You installed the Special version. Re-install the mod, but only Install the Basic version, not the Special one, and you'll get those characters.

Q: My game Crashes!
A: Install the mod, then delete Costumes2.xml. Be aware that this might cause characters to change appearence
when collecting some items.

Q: I'm in Snowy/Waterfall and the screen is pitch black!
How to fix:
Go inside resources/gfx/Background and delete the "Black" images. Those being: 8bitclouds_64,8bitclouds_64_black,8bitclouds_642,8bitclouds_643,blue_overlay and orange_overlay.

Q: I see a credits page, but not the Challenge page! Where is it?
A: If you want to see the challenges, just go inside gfx/ui/main menu and delete challengeph.png

Q: Is this compatible with Mac/Linux?
A: As far as we know, it's compatible with mac. It's super buggy with Linux and we plan on fixing of it later.

Q: I found a bug! Where can I report it?
A: Either Private Message me through Steam or the mod's blog.

Q: Can I suggest/submit stuff?
A: Yes! Either go to the mod's blog or post a comment in this comment section.

- The mod can be very glitchy on Linux and Mac.

- The Rebirth-only version is very early so expect glitches.
(Example: No Gaster Blaster. For some reason, rebirth ignores the familiar folder.)

_ In Snowy Rivershore and Waterfall, the screen might go black, but you can still hear the sound. Read the FAQ, you can find the answer there.

-Bugfix for Mac:

-More item reskins. (Taking Suggestions!)
-Waiting for Afterbirth+ !!!!

SwingPoynt v2:
iVertrox (Spanish):



Special Thanks to:
Patkall - Sprites
FAz - Sprites
SoaringSparrows - Original Concept
IKARUS - Song Credit
/u/Haylex - Tem Shop Mod
Draexzhan - Miscellaneous Item Sprites
reijigazpacho - Logo
Felix ( - Nightmare Sprites and the Omega Flowey boss
Sophomore - Miscellaneous Item Sprites
/u/otherhand42 - Miscellaneous Help
engineerthecowboy - Rebirth Testing
Toby Fox - Undertale


x 7692

- 20+ New items and 3 transformations, by the talented FAz!

- Community Update: 20+ items and a Flowey transformation, by the amazing /u/Patkall! Thank you!

- Fixed compatibility with the newest Isaac patch.

- More items

- New version whenever Afterbirth+ Hits

- Fixed Rebirth Compatibility

- Rebirth Support! (Thanks to engineerthecowboy for testing!)

- Community Made items!

- More items, like Muffet's Pet and Lil' Whimsalot!

- New character: Mad Dummy!

- Made it easier to understand how to install/know what version you're using.

- Small item replacements.

- Balanced some stuff.

- Fixed Special Version having a hybrid of Gaster and Temmie.

- Two New Characters, Gaster and Temmie.

- Two new end bosses, Omega Flowey and God of Hyperdeath Asriel

- HP up item reskins

- Some music added

- Napstablook now Starts with Dapper Blook

- Frisk starts with Purity (Soul Colors)


- Only a small amount of items now change your character.

- Asgore, Sans, Mettaton, Toriel, Asriel and Undyne have new costumes wich will help prevent their appearence to change.

- Fixed some naming stuff

- Made the Character menu less messy

- Toriel starts with proper items

- Blue womb is not dunked up anymore

- Characters don't have their items because you didn't unlock them was fixed

- Napstablook glitches when picks up a item was fixed

- Frisk doesn't have Isaac's heart, just <3

- Papyrus lost 1 heart container inside his spaghetti

- Mettaton has better bombs and Tech.5 (not tech 2)

Try and add Gaster! just a suggestion
For some reason it downloads as an internet file ...why??? I am really confused! Am I the only one with this problem?
I can't delete it from my mods. Can somebody please help me!


i was posting a comment

and then a fly
Undertales dead make some more fun stuff.
Like a game with the mod and other mods
Suit yourself, I think this mod is quite nice myself.
I tried downloading it, I opened the file and it told me it cant open ".rar" files. Please help?
You need to understand what the .rar format is first. When you make a .rar file, you can add multiple files into that rar file, kind of like a library of books, if each file is a book, a .rar file is a library containing multiple books. The .rar format isn't only there for putting multiple files or "books" into a single .rar or "library" but it also compresses the actual size of the book. Meaning if you have one file that's 10MB in size and you add it to a .rar archive, the .rar algorithm will attempt to compress the size, so then you'll end up with a .rar archive 6MB in size rather than 10MB since the .rar algorithm compressed the file to make it smaller. Since the mod contains a lot of files, it's a lot easier to put all the files into a single .rar file rather than offering a download for each file individually, that and it also compresses the size of the mod from 90MB to 80MB so it's faster to download. Anyways, to extract the files or "books" from a .rar file or "library" you need a separate program to extract it, it's not hard to do. There are two good programs that exist for this: WinRAR, and 7Zip. Download one of these and extract the .rar file using it.
i really did this mod I would like to suggest a item maybee for a future update? the item was mettaton's bomb as a follower that shots a bomb when you shot tears randomly
Can you add temmie as playable character?
What the Heck Is Happening With my Game?! Its So Buggy Right now i Can't See Right, When Drop a Penny Or Bomb Bugs A lot, Mad Dummy Its With Isaac's Face, Undyne Its Without a Eye And She Is Bald Now And Dont Have Her Spear,Doesn't have Alphys,Asgore Dont have a Beard Or Crown,Gaster Bugs When Die Or Take a Hit.
Thats It
i think alphys is only in afterbirth. don't quate me on that I don't remember
For some reason the head of the Mad Dummy is just Isaac's head and the skin tone is pitch black, FYI i'm using the Rebirth Version of this mod. Is there something i did wrong when i was installing? it or is it a glitch?
hi I think it would be cool if you added metaton the game
they did... as an item (forgot the name) and as the cathedral boss (Mettaton NEO) (to unlock cathedral you need to beat "mom's heart" 11 times) to unlock mom's heart beat "mom" (waterfall 2 or (if vanilla A.K.A no mods) abyss/ the depths 2)
w the only thing missing from mettaton for me is glitter bombs. I saw a vid where someone got a book that spawns bombs. and they always got batteries. they ended up fighting mega satan and filling THE ENTIRE ROOM with items and just pressing space. it was beautiful. also props for being so helpful in coments with the telling of ho to do things. I mean I wwknew already but that's still pretty nice of uw
what folder do you put the mod file in????? i am new at mods for isaac
January 20, 2017 - 7 months ago

A new animated Planetarium theme (from Antibirth) is now available!

There is a new DLC search filter on the Browse Mods page.

Added the 50 new babies from Afterbirth+.

The What's New sheet will try to get your attention when there is a new site update.

Fixed some mod icons not changing after being updated.