diff --git a/docs/arcturus/01-index.md b/docs/arcturus/01-index.md
index b0983d49..00be88d7 100644
--- a/docs/arcturus/01-index.md
+++ b/docs/arcturus/01-index.md
@@ -36,7 +36,9 @@ This section is a placeholder. If you know anything about the topic, please help
 
 ## File Formats
 
-The following file types have been found in the Japanese DVD release of Arcturus:
+The following file types have been found in the Japanese DVD release of Arcturus (TODO: Add hash of the PAK files? There aren't that many versions...):
+
+TODO: Shared file formats -> link to RO overview or combine both and add to landing page/link from there?
 
 ```txt title=arcturus-jp-extensions.txt
 act
diff --git a/docs/file-formats/01-index.md b/docs/file-formats/01-index.md
index 5c49b9b4..7324b4e4 100644
--- a/docs/file-formats/01-index.md
+++ b/docs/file-formats/01-index.md
@@ -61,3 +61,116 @@ Here's a list of the atomic data types that you may encounter in the layout tabl
 |  `array`  | variable |           Fixed-size array of structures or values; the exact size depends and may only be implicit           |
 
 Please note that in many cases the exact type is unknown and can only be guessed, based on examples found "in the wild".
+
+## Ragnarok File Formats
+
+Gravity created a number of custom file formats for [Arcturus](/arcturus), which they later adapted for the RO client.
+This documentation differentiates between them only as far as is necessary to understand their many unused (and oftentimes strange) features.
+
+### Asset Containers
+
+Bundling many small files in a [BLOB](https://en.wikipedia.org/wiki/Object_storage) "archive" can help minimize the disk footprint and speed up loading times:
+
+- [GRF](/file-formats/GRF): Most of the game assets are stored in this large storage container, potentially compressed and/or encrypted
+- [RGZ](/file-formats/RGZ): The RO client includes a "Patch Client" that downloads most updates in this compressed storage format
+- [GPF](/file-formats/GPF): Another extension used the the game's updater, which however seems to just be an alias for GRF files
+- [PAK](/file-formats/PAK): Arcturus and early RO clients use a different format, the origins of which aren't quite clear to me at this time
+
+Although modern SSDs have different performance characteristics than mechanical HDDs, the game continues to rely on asset containers as a virtual file system. Most frequently-accessed files must therefore be extracted in-memory or on disk.
+
+### Raster Images
+
+A combination of standard and custom-made image formats see use in the RO client:
+
+- [BMP](https://en.wikipedia.org/wiki/BMP_file_format): Most of the sprites and textures mapped to 3D geometry exists as raw bitmap
+- PAL: They're lookup tables that store [palette](<https://en.wikipedia.org/wiki/Palette_(computing)>) colors for the indexed-color image formats
+- [TGA](https://en.wikipedia.org/wiki/Truevision_TGA): Truecolor images with transparency exist for many effects and some monster sprites
+- [JPG](https://en.wikipedia.org/wiki/JPEG): These appear to be fairly rare, but in a few instances JPEG textures were assigned
+- [EBM](/file-formats/ebm): Guild emblems are also bitmaps, but the RO client compresses them first
+
+Other formats may include image data as well, but it's usually combined with other metadata.
+
+### Map Definitions
+
+- Map files: RSW, GND, GAT
+
+### 2D Sprites
+
+- 2D sprites and effects: SPR, ACT, , IMF, , STR, EZV (, , )
+
+### 3D Models
+
+TODO: RSM, RSM2, GR2, Arcturus (RMA?)
+
+- 3D models: RSM, RSM2, GR2 (see RAD website)
+
+### Multimedia
+
+Although both games contain various multimedia formats, they will not be fully specified here:
+
+- [WAV](https://en.wikipedia.org/wiki/WAV): Sound effects and music-like jingles/songs utilize the waveform audio format
+- [MP3](https://en.wikipedia.org/wiki/MP3): All of the background music ("BGM") tracks use this standard audio format
+- [BIK](/file-formats): Video textures in [Bink](https://www.radgametools.com/bnkmain.htm) format; introduced recently and so far extremely niche
+- [ADP](/file-formats/adp): Arcturus stores its music tracks in [ADPCM](https://en.wikipedia.org/wiki/Adaptive_differential_pulse-code_modulation) format, with a fairly arcane codec
+
+
+### Miscellaneous
+
+Anything that doesn't fit the above criteria - most of these aren't particularly relevant:
+
+- Scripts: Lua and LUB (see Lua website)
+
+```sh
+      1 bak
+      1 bat
+      1 egg
+      1 fds
+      1 flc
+      1 mp3
+      1 pptx
+      1 rsx
+      1 scp
+      1 zip
+      2 ase
+      2 scc
+      2 tmp
+      3 bson
+      3 log
+      4 gif
+      4 psd
+      4 sfk
+      4 xml
+      5 bik
+     16 lua
+     21 gr2
+     23 fna
+     64 db
+     91 ezv
+    114 txt
+    305 imf
+    392 jpg
+    449 png
+    453 lub
+    987 gnd
+    988 gat
+    988 rsw
+   1733 rsm2
+   2716 str
+   3103 wav
+   3676 pal
+   7048 rsm
+   7565 tga
+  39505 spr
+  46583 bmp
+  54845 act
+```
+
+See https://github.com/RagnarokResearchLab/ragnarokresearchlab.github.io/issues/92#issuecomment-1858732921
+
+Most of this is probably garbage - double-check just to be safe?
+
+Also check Arcturus? (Maybe later...)
+
+---
+
+TODO old README, maybe separate page