I've only managed to unpack the 'Game.rgss2a' where you'll find the Data file and you can edit the 'rvdata' files such as 'Weapons.rvdata' within that with a programme. Can't remember which programme that was, but an easy search should do it.
Apprently using 'RPG Maker VX' then can repack / archive these files back into an 'rgss2a'. I am assuming you would replace the original 'Game.rgss2a' file.
This isn't exactly a working science at the moment, or a trainer, but it gives you an idea of the process I've looked at.
Update.....
I managed to edit the complete game using a file which can be found on the internet - RPG_Maker_VX_102_ENU_SSG
You will also need a file called 'All Decrypter' - which the exe file will be 'RPG Maker Decrypter'
Use RPG Maker and start a new 'Project 1' and just save this.
Go to the main Amber Throne folder which you'll need to use All Decrytor for the "Game.rgss2a' file and this will extract files/folders into the 'Extract Folder'.
Copy / Cut and Paste the extracted files/folders from the All Decryptor into the 'Project 1' folder.
Copy / Cut and Paste the other files/folder from the main Amber Throne folder into the 'Project 1' folder EXCEPT the original 'Game.rgss2a' file.
Open up 'Game.rvproj' which will automatically launch the RPG Maker where you will find on the top main tabs, Database/s.
Edit your heart out and save.
**Tip - don't go crazy like I did with the weapons editing and add all the 'States to Add' or it will take ages every time you go into battle'.
The game can be launched in the RPG Maker - Green Arrow Button or 'Game.exe' file in the Project 1 folder.
Happy Gaming!