You gain the full knowledge and proficiency to materialize and build all of the technology and science shown in the Warhammer Fantasy universe.
From the Skaven's infernal designs, to the Dwarfs' ingenious schematics, to even the Old Ones' far reaching devices and machines that they bestowed upon the Lizardmen, you know it all.
If you are in the Warhammer Fantasy universe, and any of the races knew that you are a massive encyclopedia of every technology in their universe, then be prepared to have a really strong backer, else kidnapping and torture is a certain possibility.