EFX0011: Libra effect files

Source: docs/formats/efx.md
SHA-256: b94b3164…7de11eca

Contents

Wrapping · Header · Chunks · Resources · How the game reads it · Rebuilding · Leads

An effect: the textures, sound banks and other resources it uses, and its sets of chunks with their data, as a list of chunks after a 16-byte header. Every .efz file under effect/ is one, wrapped in MLZ0 (LZ4); effect/global/common/c_all.efz holds the shared battle effects (655 sets), every other .efz one effect with one or more variants. The game parses it with the effect player of its Libra library (Libra\TsMalloc.cpp); how an effect is picked and loaded is in Effects. This doc names the format after the magic the game checks.


Based on	Every `.efz` file under `effect/`: 2,085 files (`global/common/c_all.efz`, 51 in `global/magic/`, 8 in `global/chr_make_god/`, and 2,025 in the eight language folders `<lang>/{chr_make,event,results,title,victory}/`); the unpacked executable, SHA-256 `7b0230a11498f40396c9048345e7cfe0ef442cb7ca8faffc6f197920d2669599`; the LZ4 block format (lz4_Block_format.md, checked 2026-10-11).
Checked	2026-10-11
Method	Single-file C# programs (session scratchpad, `effect/scan.cs` and `effect/recompress.cs`): an LZ4 block decoder that unwraps every file and checks the sizes, then a walk of every chunk of every file; re-compressing every payload with K4os.Compression.LZ4 1.3.8. Static analysis with Ghidra 12.1.4 of the loader (`0x1404ab460`) and the chunk readers, through the decompiled code in `local/exe/decomp/`; `xxd` of the executable. Not yet decoded or rebuilt by the toolchain; no in-game tests.

Wrapping

The file on disk is MLZ0 (containers.md), not RotXor or ZIP.

Offset	Size	Type	Name	Meaning	Confidence	Source
0x0	4	raw[4]	`magic`	`MLZ0`. The game doesn't check it.	confirmed	C# scan, all 2,085; not read by `0x1401a2a00` (containers.md).
0x4	4	u32	`size`	Size of the effect once unpacked. The game allocates exactly this much and parses that many bytes.	confirmed	C# scan: every file unpacks to exactly this size, all 2,085; `0x1401a29e0`, `0x140415190`.
0x8	file size − 8	raw[n]	`block`	One LZ4 block (no frame header, no checksum) that runs to the end of the file.	confirmed	C# scan: the decoder uses up exactly file size − 8 bytes in all 2,085; `0x1401a2a00` (`LZ4_decompress_safe` of size − 8 bytes).

confirmed: LZ4's default compressor (LZ4_compress_default, acceleration 1) gives back every block byte for byte. Source: K4os.Compression.LZ4 1.3.8 at L00_FAST, 2,085 of 2,085 identical.

The unpacked effect starts with 16 bytes.

Offset	Size	Type	Name	Meaning	Confidence	Source
0x0	8	raw[8]	`magic`	`EFX0011` and a NUL. The game compares all 8 bytes and loads nothing from a file that differs.	confirmed	C# scan, all 2,085; `0x1404ab460` (compares with the 8 bytes at `0x140696F90`, which `xxd` shows are `EFX0011\0`).
0x8	4	f32	`unk_0x8`	1.0 in every file. The loader doesn't read it.	confirmed	C# scan, all 2,085; not read by `0x1404ab460`.
0xC	4	u32	`total_size`	The effect's size, equal to the wrapper's `size` in every file. The loader goes by the buffer's size instead.	confirmed	C# scan, all 2,085; `0x1404ab460` (ends at buffer + the size it is given).

Chunks

From 0x10 to the end the file is a list of chunks, each starting with a 12-byte header.

Offset	Size	Type	Name	Meaning	Confidence	Source
0x0	4	u32	`size`	The chunk's size, header included. A multiple of 16 in every chunk.	confirmed	C# scan, all 123,067 chunks.
0x4	2	u16	`unk_0x4`	`0x100` in every chunk. The loader skips a chunk where it isn't.	—	C# scan; `0x1404ab460`.
0x6	2	u16	`type`	What the chunk holds: Chunk types.	confirmed	C# scan; `0x1404ab460`, `0x1404ab220` (dispatch on it).
0x8	4	u32	`unk_0x8`	An offset that the loader hands to the chunk's reader (in the global at `0x140F3B2A0`), which uses it to find a second part of the data. `size` − 16 in most chunks; larger gaps in `0x700`, `0x800` and `0xA00` chunks.	guess	`0x1404ab460`; the readers `0x1404a4920`, `0x1404a51f0`, `0x1404a7250`, `0x1404a75b0`; C# scan (values).
0xC	`size` − 12	raw[n]	`data`	The chunk's data.	confirmed	C# scan.

confirmed: the chunks follow each other with no gaps, the first at 0x10 and the last ending exactly at the end of the effect. Source: C# scan, all 2,085 files.
likely: they have to: the loader stops only when a chunk ends exactly at the buffer's end, so a size that runs past it makes it read beyond the buffer. Source: 0x1404ab460.
confirmed: the order in every file is the resource chunks (0xB00, when there are any), then sets (a 0x600 followed by its 0x610/0x620 pairs, once per set), then the 0x700, 0x800 and 0xA00 chunks, each type together. Source: C# scan.

Chunk types

The first bytes of each chunk's data say what it belongs to. Counts are over all 2,085 files.

Type	Chunks	What it is	First bytes of `data`	Confidence	Source
`0x600`	2,873	A set: one playable effect (a variant).	u16 set ID, 1, 2, 3, … in file order.	confirmed (IDs); likely (role)	C# scan; `0x1404a4a70` (files the set at its ID), `0x1404a49b0` (up to 1,024 sets).
`0x610`	17,225	Chunk `0x610`: a child of the set before it, in one of the set's 32 slots.	u16 set ID (always the current set), u8 slot (under 32).	confirmed (set ID); likely (role)	C# scan; `0x1404a4d10`, `0x1404a4080` (32 slots).
`0x620`	35,218	Chunk `0x620`: a child of a `0x610`, filed under it by slot.	u16 set ID, u8 `0x610` slot, u8 slot.	likely	`0x1404a4920`, `0x1404a4860`.
`0x700`	2,445	Chunk `0x700`, filed in a table by index; guess: animation or particle data.	u16 index, u8.	guess	`0x1404a51f0` (table at `0x140F33D00`), `0x140503d10`.
`0x800`	26,058	As `0x700`, another table.	u16 index, u8.	guess	`0x1404a7250` (table at `0x140F33D10`), `0x140506e90`.
`0xA00`	25,628	As `0x700`, another table of up to 1,023 entries.	u16 index, u8.	guess	`0x1404a75b0` (table at `0x140F33D28`, cleared over 1,023 entries by `0x1404a72b0`), `0x140507240`.
`0xB00`	13,620	A resource: texture, sound bank or another kind (Resources).	u16 resource ID, u8 kind, u8 index.	confirmed (fields); likely (role)	C# scan; `0x1404a84f0`.

likely: the loader also reads chunk types 0x500–0x540, 0x601, 0x611, 0x900 and 0x1000, which no shipped file has. 0x1000 runs one command of a small command set (0x14050dfe0). Source: 0x1404ab220; C# scan (no such chunk).
likely: the game uses each chunk in place, as its live data: the set reader copies the set ID to data 0x38 and zeroes data bytes 0x3C–0x13B of a 0x600 chunk, and the other readers write fields inside their chunks. So each chunk type's data must be at least its full size. Source: 0x1404a4a70, 0x1404a51f0, 0x1404a7250, 0x1404a75b0; How the game reads it. confirmed: the files already hold those values: the set ID at data 0x38 and zeros at 0x3C–0x13B in all 2,873 0x600 chunks. Source: C# scan.

Resources

A 0xB00 chunk's data starts with a 4-byte key: u16 resource ID (0 in every chunk), a kind letter, and an index from 1. confirmed: no file has two resources with the same key. Source: C# scan.

Kind	Chunks	What it is	Confidence	Source
`P`	3,374	Kind `P`, unknown; guess: a mesh (vertex positions, texture coordinates and a colour).	guess	Hex inspection; `0x14050c2f0`, `0x14050c9a0`.
`Q`	251	Unknown.	—	`0x14050d1a0`, `0x14050d200`.
`R`	9,637	A texture, as below.	confirmed	C# scan; `0x140507720`, `0x1405077e0`; `0x1404a8760` (finds an `R` resource by name).
`S`	0	Unknown; read by the game, in no file.	—	`0x14050c0d0`, `0x14050c160`.
`T`	277	Kind `T`, unknown; guess: a mesh with an index count and vertex positions.	guess	Hex inspection; `0x140508df0`, `0x14050bd20`.
`W`	81	A sound bank, as below.	confirmed	C# scan; `0x14050d500`.

likely: a resource whose key is already loaded is updated rather than added, and any other kind is ignored. Source: 0x1404a84f0.

`R`: texture

Offsets are from the start of the chunk's data.

Offset	Size	Type	Name	Meaning	Confidence	Source
0x00	4	raw[4]	`key`	Resource ID 0, `R`, index.	confirmed	C# scan.
0x04	4	u32	`unk_0x04`	1 in every texture.	confirmed	C# scan, all 9,637.
0x08	4	u32	`width`	Width in pixels; the same as the `btx`'s.	confirmed	C# scan: equal in all 9,458 with a `btx`.
0x0C	4	u32	`height`	Height in pixels; the same as the `btx`'s.	confirmed	C# scan, as above.
0x10	4	f32	`unk_0x10`	1.0 (3,340), 2.0 (9), 4.0 (6,281) or 8.0 (7).	confirmed (values)	C# scan.
0x14	4	u32	`btx_size`	Size of the `btx` that follows; 0 for a placeholder. The chunk header's `unk_0x8` is `btx_size` + `0x40` in every texture.	confirmed	C# scan, all 9,637.
0x18	32	raw[32]	`name`	The texture's name, each byte XORed with `0xAB`, padded with `0xAB` (a NUL once decoded): `chr_make_word_1_00`, `card_normal`, …	likely	C# scan (every name read decodes to text); `0x1404a8760`.
0x38	`btx_size`	raw[n]	`btx`	The texture, a `btx` (starts `btx\0`).	confirmed	C# scan: at `0x38` in all 9,458 with `btx_size` > 0.
0x38 + `btx_size`	to the chunk end	raw[n]	`tail`	12 bytes in 7,588 textures, up to 5,644 in the rest. Unknown.	confirmed (sizes)	C# scan.

confirmed: 179 textures have btx_size 0 and no image: 176 named __dummy__card_normal, and __dummy__god_00–02. Source: C# scan.
likely: these are slots the game fills at run time: character creation copies the texture named card_normal from one loaded effect into __dummy__card_normal of another, and builds __dummy__god_%.2d names the same way. So these names have to stay as they are. Source: 0x1404afcc0 (0x140412220 → 0x1404a8760, by name).

`W`: sound bank

Offset	Size	Type	Name	Meaning	Confidence	Source
0x00	4	raw[4]	`key`	Resource ID 0, `W`, index.	confirmed	C# scan.
0x04	4	u32	`bank_id`	5000–5066; 5031 is in 11 files, 5032 in 8, the rest in one.	confirmed (values)	C# scan, all 81.
0x08	4	u32	`unk_0x08`	0 in the files. The game writes the bank's handle here once it's registered.	likely	C# scan; `0x1404a87e0` (stores the result of `0x140285930`).
0x0C	4	u32	`sabf_size`	Size of the bank.	confirmed	C# scan: the chunk ends 4 bytes after it in all 81.
0x10	`sabf_size`	raw[n]	`sabf`	The sound bank (starts `sabf`).	confirmed	C# scan, all 81.
0x10 + `sabf_size`	4	raw[4]	`padding`	To the chunk end.	confirmed (size)	C# scan.

likely: the game registers the bank with the sound system (0x140285930) and keeps bank_id and the handle in a table of 64 entries. Source: 0x1404a87e0, 0x1404a87b0.

How the game reads it

Every fact here is static analysis of the unpacked executable, so at most likely; the functions are in Effects.

likely: once the MLZ0 file is unpacked, the game calls the loader (0x1404ab460) with the buffer and the wrapper's size. It compares the 8-byte magic and returns without loading anything if it differs; it reads neither unk_0x8 nor total_size. Source: 0x1404141f0 (c_all.efz), 0x140414fe0 (every other effect).
likely: it walks the chunks from 0x10, by size, until one ends exactly at the end of the buffer. A chunk whose unk_0x4 isn't 0x100 is skipped. Runs of 0x600/0x610/0x620, 0x700, 0x800 and 0xA00 chunks are each handed to their reader as one block; every other chunk goes to 0x1404ab220, which picks the reader by type and ignores unknown types. Source: 0x1404ab460, 0x1404ab220.
likely: both effect loaders set a flag (bit 3 of byte 2 of the effect's resource) that makes the loader use the chunks where they are, in the unpacked buffer, which is kept until the effect is freed. Without the flag it would copy each run into memory of its own, 16 bytes at a time. Source: 0x1404141f0, 0x140414fe0, 0x1404ab460, 0x1404ab1b0.
likely: there are no CRCs or checksums, and no count of chunks or sets in the header: what the game needs is the right sizes (the wrapper's size, each chunk's size) and well-formed chunks. Source: the functions above.

Rebuilding

confirmed: wrapping the unpacked effect back as MLZ0 (the magic, size, then the block from LZ4's default compressor) gives back every original file byte for byte. Source: C# scan with K4os.Compression.LZ4 1.3.8, 2,085 of 2,085.
likely: the game would also take any other valid LZ4 block, since it decompresses with LZ4_decompress_safe and checks nothing else; but the file's size in FileTable.bin must be exact, because the game takes file size − 8 as the block's length (filetable.md).
likely: a rebuilt effect keeps the header as it is, every chunk's size a multiple of 16 and exact, unk_0x4 0x100, the set IDs 1, 2, 3, … in order, and the texture names that game code looks up (R: texture).

Leads

The data of each chunk type: the set (0x600), its children (0x610, 0x620) and the 0x700, 0x800 and 0xA00 layouts, starting from their readers (0x1404a4a70, 0x1404a4d10, 0x1404a4920, 0x140503d10, 0x140506e90, 0x140507240) and the frame-timed tracks at 0x1404a2d90. What unk_0x8 in the chunk header points at in each type.
The resource kinds P, Q and T, and what follows a texture's btx (tail).
Whether a texture's unk_0x10 (1.0–8.0) is a scale for the image.
Emitters: bl::efx::Emitter is a game class, but of another system: no code in the Libra regions (0x1404a2c60–0x1404aba48, 0x140500d60–0x14050e77e) calls into a bl::efx region, so chunks 0x610/0x620 keep positional names until their readers show what they are.
"Effect" means two things in the game: visual effects (effect/, EffectManager.cpp; vfx) and skill effects (EFFECTTEXT_LC_EFFECT_*); this doc is about the first.
The command set of chunk type 0x1000 (0x14050dfe0, opcodes 0–5, 8–13, 17, 19–21, 23 and 25–28, one command per call): no shipped effect uses it, so it matters only to a mod that adds one.
The btx textures and sabf banks inside effects are the same formats as elsewhere in Data/; their docs cover them.