Catalog Files (*.CAT)

Darklands stores game assets in catalog files - simple archive containers, each holding a set of related files. There is no single monolithic pack file; assets are split across multiple named catalogs.

Extension: *.CAT — also extensionless: BC, LCASTLE, MSGFILES
Location: Game root
Byte order: Little-endian (16/32-bit)
Size: Variable — 24-byte directory entries + raw payloads
Compression: None — payloads embed their own formats (DRLE, PIC, etc.)
Magic: None
Status: Documented
Source: Wendigo — X.cat.xml

Canonical source: X.cat.xml (Wendigo’s Darklands repo)

Known Catalog Files

Filename	Contents
`A00C.CAT`	Battle sprites for a tall, thin alchemist (“Hans” from the default party)
`C00C.CAT`	Battle sprites for a short, wide cleric (“Ebhard” from the default party)
`E00C.CAT`	Battle sprites for human enemies
`F01C.CAT`	Battle sprites for a male fighter (“Gunther” from the default party)
`F60C.CAT`	Battle sprites for a female fighter (“Gretchen” from the default party)
`M00C.CAT`	Battle sprites for non-human enemies
`EINFO.CAT`	Enemy info display images (PIC files)
`IMAPS.CAT`	Map tile graphics
`BC`	Combat tile art - 65 entries, seven tile families, battle environment graphics (see below)
`LCASTLE`	(extensionless catalog - slightly corrupt, last entry is zero-length)
`MSGFILES`	All text option menus and situation descriptions (`.msg` files)
`EDITOR.CAT`	Character editor images (not present in version 1.07)

Battle sprite catalogs contain three animation types, identified by the 4th-5th letters of the filename:

Suffix	Description
`CB`	Combat animations (many weapon variants)
`WK`	Walking animations
`DY`	Dying / dead animations

File Format

Each catalog is a flat directory followed by file data.

Top-Level Layout

Offset 0x00:  word         num_entries  - number of files in this catalog
Offset 0x02:  entry[0..n]  entries      - array of 24-byte directory entries
              ... (file data at offsets specified in entries)

Directory Entry (24 bytes)

Offset	Size	Field	Description
+0x00	12	`filename`	8.3 DOS filename, null-padded to 12 bytes
+0x0c	4	`entry_metadata`	Native 24-byte catalog-entry metadata field; often timestamp-like, but not yet proven universal
+0x10	4	`length`	Length of file data in bytes
+0x14	4	`offset`	Byte offset from start of catalog to file data

Metadata notes: In most ordinary CAT-family archives (A00C.CAT, BC, C00C.CAT, E00C.CAT, EINFO.CAT, F01C.CAT, F60C.CAT, IMAPS.CAT, LCASTLE, M00C.CAT), this field decodes cleanly as a plausible clustered DOS-style date/time value. MSGFILES is the main exception: it keeps the same structural field, but the values span a wider range, cluster by filename family, and collide across unrelated message families.

The generic executable resource-open/read path uses the filename, size, and payload offset fields, but does not currently appear to consume the 0x0C dword directly. So the safest interpretation is:

it is native archive metadata in the 24-byte entry layout
timestamp remains a useful working interpretation for many CAT-family archives
its exact semantics may vary by catalog family and should not yet be treated as universally proven

BC Archive - Combat Tile Art

BC is an extensionless catalog with 65 entries and a total uncompressed payload of 189,815 bytes. It contains all the tile art for combat encounters, organised into seven families:

Suffix	Count	Content
`FLC`	9	Floor tiles, lit (combat)
`FFC`	9	Floor tiles, far (ceiling / distance)
`NWC`	9	Near-wall tiles
`NFC`	9	Far-wall tiles
`WWC`	9	Wide-wall tiles
`WFC`	9	Wide-far-wall tiles
`FRC`	9	Filler / trim tiles

Seven families x 9 variants = 63 tile entries. The remaining 2 entries are structural (index header and null entry).

The 9 variants per family cover the five combat environment types plus special cases:

Environment	Tile set name pattern
Outdoor (Wild)	`OUT.*`
Mine	`MINE.*`
City	`CIT` / `URB`
Fort	`FORTMONS.*`
Tomb / Cave	`KEEP.` and `CAVEDRAG.`

All five environment bundles are confirmed - their filenames appear in the archive directory and have been extracted and matched to their contexts. The environment selection string bank lives in section 138 of DARKLAND.EXE at flat offset 0x17F670.

IMAPS - Encounter Grid

Also used by the combat system is the IMAPS.CAT catalog, which contains the encounter map grid data:

1,109 records of 12 bytes each, plus a 20-byte header
Total: 20 + 1109 x 12 = 13,328 bytes
The records encode a 33 x 33 tile grid (1,089 cells), with the remaining 20 records used for supplementary lookup data
Each 12-byte cell describes tile type, height, wall flags, and passability for one grid position

The IMAPS grid is a static lookup table, not procedurally generated. Every combat map in Darklands is built from IMAPS cell data combined with BC tile art.

Streaming Read Pipeline

For large assets, the engine can read resource data incrementally from a catalog instead of loading the entire payload at once:

resource_init_reader
    -> stores catalog file handle in 0x8e30
    -> installs resource_read_chunk as callback at 0xeeb8

resource_read_chunk  (called when buffer empty)
    -> reads next chunk from catalog
    -> fills buffer at 0xeffc
    -> updates stream read pointer at 0xf1fc

This appears to be a generic streamed resource-input path used by the engine. It should not be confused with the compression format of .CAT itself.

Important: .CAT files are not compressed containers. They are flat archives holding raw file payloads. Compression, when present, belongs to the embedded file format:

.IMC uses Darklands DRLE
.PIC uses its own image compression pipeline
.MSG files are structured text data, not compressed by the catalog