MHP3 Custom Quest Creation Kit

A complete toolkit to create custom quests for Monster Hunter Portable 3rd (PSP / ULJM05800) entirely on a PC, merge them into the event-quest save MHP3RD.BIN, and distribute them freely. The Chinese MHP3TaskEdit editor and the crypto tools were reverse-engineered, translated (JP/EN), modernised and automated.

Download the kit(.zip 約2.1MB)

Read first (important)

The kit contains no game data (no ROM/ISO). You must own MHP3rd yourself.
The game-specific key gamekey.bin is NOT included; you must obtain it yourself to build BINs (see below).
Use modded saves at your own risk. Online (ad-hoc) use is NOT allowed.
Always back up your save data before working.

What can it do?

Edit a quest's star rank, type, map, time limit, rewards, continuation, monsters (species/size/HP/attack/defense/stamina), supplies, gathering, material rewards and quest text. MHP3RD.BIN is doubly encrypted (PSP save crypto + MH's own crypto); both layers were analysed and verified to be processable on a PC, and the edit → encrypt → build-distributable-BIN flow is automated.

What's included

Folder / file	Description
MHP3TaskEdit_日英版/	Main editor (recompiled & bilingual MHP3TaskEdit) with a quest-list sidebar: open a BIN, edit, and build a distributable BIN in one go.
BIN化ツール/	Layer-A crypto (endecrypter.exe) + automation pipeline and PAT/data.bin scripts + a sample plaintext BIN.
endecryptQST/	Layer-B crypto tool (driven automatically by the pipeline).
仕様書.md	Full specification, usage and analysis notes.
企画書_53クエスト.md	53 designed custom quests with tool input values.

Requirements

Windows (no PSP hardware needed)
.NET Core 3.1 Desktop Runtime (for MHP3TaskEdit)
Python 3 + pip install pywinauto capstone pycryptodome (for the BIN automation)
PPSSPP (to play on PC) or a CFW PSP

gamekey.bin (not included)

Building/decrypting MHP3RD.BIN needs the 16-byte save key for ULJM05800. As a game-specific secret, it is not bundled. Obtain it one of these ways and place it at BIN化ツール/gamekey.bin:

On a CFW PSP enable the SGKeyDumper (or SGDeemer) plugin → save/load MHP3 → ms0:/PSP/GAME/SED/gamekey/ULJM05800QST.bin appears; rename it to gamekey.bin.
Or obtain the key shared in the old MHP3 modding community. Do not redistribute the key — it is game-specific.

Note: a finished MHP3RD.BIN is common to all PSP/PPSSPP, so it works on anyone's save and can be distributed (the key itself is never distributed).

Two ways to play

Route A (easiest, no PSP crypto): CWCheat PAT

Export a .pat cheat from your quest → load it via PPSSPP/CWCheat → load an event quest in the gathering hall → turn the PAT on → select the quest. No BIN editing needed.

Route B (build a distributable BIN): data.bin → MHP3RD.BIN

Build the BIN via the MHP3TaskEdit sidebar or `mhp3bin_auto.py build`, then place it in PSP/SAVEDATA/ULJM05800QST/. Anyone can use the same BIN, and anyone can build their own with the same steps.

See the bundled 仕様書.md and the README files for full instructions.

Download the kit(.zip 約2.1MB)

Notice & disclaimer

The kit contains no game content. Each tool's copyright belongs to its respective author.
gamekey.bin is a game-specific secret; do not redistribute it publicly.
Use modded saves at your own risk; no online use; always back up important saves.

Back to MHP3 guide

MHP3 Custom Quest Creation Kit

Download the kit(.zip 約2.1MB)

Read first (important)

The kit contains no game data (no ROM/ISO). You must own MHP3rd yourself.
The game-specific key gamekey.bin is NOT included; you must obtain it yourself to build BINs (see below).
Use modded saves at your own risk. Online (ad-hoc) use is NOT allowed.
Always back up your save data before working.

What can it do?

What's included

Folder / file	Description
MHP3TaskEdit_日英版/	Main editor (recompiled & bilingual MHP3TaskEdit) with a quest-list sidebar: open a BIN, edit, and build a distributable BIN in one go.
BIN化ツール/	Layer-A crypto (endecrypter.exe) + automation pipeline and PAT/data.bin scripts + a sample plaintext BIN.
endecryptQST/	Layer-B crypto tool (driven automatically by the pipeline).
仕様書.md	Full specification, usage and analysis notes.
企画書_53クエスト.md	53 designed custom quests with tool input values.

Requirements

Windows (no PSP hardware needed)
.NET Core 3.1 Desktop Runtime (for MHP3TaskEdit)
Python 3 + pip install pywinauto capstone pycryptodome (for the BIN automation)
PPSSPP (to play on PC) or a CFW PSP

gamekey.bin (not included)

Building/decrypting MHP3RD.BIN needs the 16-byte save key for ULJM05800. As a game-specific secret, it is not bundled. Obtain it one of these ways and place it at BIN化ツール/gamekey.bin:

On a CFW PSP enable the SGKeyDumper (or SGDeemer) plugin → save/load MHP3 → ms0:/PSP/GAME/SED/gamekey/ULJM05800QST.bin appears; rename it to gamekey.bin.
Or obtain the key shared in the old MHP3 modding community. Do not redistribute the key — it is game-specific.

Note: a finished MHP3RD.BIN is common to all PSP/PPSSPP, so it works on anyone's save and can be distributed (the key itself is never distributed).

Two ways to play

Route A (easiest, no PSP crypto): CWCheat PAT

Export a .pat cheat from your quest → load it via PPSSPP/CWCheat → load an event quest in the gathering hall → turn the PAT on → select the quest. No BIN editing needed.

Route B (build a distributable BIN): data.bin → MHP3RD.BIN

Build the BIN via the MHP3TaskEdit sidebar or `mhp3bin_auto.py build`, then place it in PSP/SAVEDATA/ULJM05800QST/. Anyone can use the same BIN, and anyone can build their own with the same steps.

See the bundled 仕様書.md and the README files for full instructions.

Download the kit(.zip 約2.1MB)

Notice & disclaimer

The kit contains no game content. Each tool's copyright belongs to its respective author.
gamekey.bin is a game-specific secret; do not redistribute it publicly.
Use modded saves at your own risk; no online use; always back up important saves.

MHP3 Custom Quest Creation Kit

What can it do?

What's included

Requirements

🔑 gamekey.bin (not included)

Two ways to play

Notice & disclaimer

MHP3 Custom Quest Creation Kit

What can it do?

What's included

Requirements

🔑 gamekey.bin (not included)

Two ways to play

Notice & disclaimer

gamekey.bin (not included)

gamekey.bin (not included)