Toggle SpoilerNote: If you have ever installed another mod that changes the chest inside the Heroes Guild Demon Door, or edited it yourself, then this will most definitely mess that edit up.
1. Download Hood and Mask Package.fmp, Mask Alpha.big and DemonDoor_Guild.tng.
2.Download ShadowNet Fable Explorer (I havn't ever used any other kind other than ShadowNet so I don't know how they work) if you haven't already and open it.
3. Go to File and Load Fable Mod Package
4. Select Hood and Mask Package.fmp and OK
5. Right click textures.big in the top left corner of Fable Explorer and hit Merge BIG
6. Select Mask Alpha.big and OK
7. Now, double click FinalAlbion.wad in the top left area of Fable Explorer
8. Hit the plus button next to 0 in the left section.
9. Find and double click Data\Levels\FinalAlbion\DemonDoor_Guild.tng NOT .lev
10. See where it says Entry Data on the new window? Hit Import in that section, NOT in the Sub Header Section. So hit the bottom import, not the top one.
11. Select DemonDoor_Guild.tng and OK and make sure to hit Apply Changes under Import!
12. Now hit Actions and Save Mods and Run Fable and you should find all 3 objects in the Chest inside the Heroes Guild Demon Door (The Library Arcanum).
Post-Note: If you install and reinstall the game, you will have to do this process again, just like any other mod you install or texture change you make, also, if you want to spawn the objects somewhere else, search up a guide on Chest Spawning or editing Shop Keeper inventories to buy it in a store.