For the next couple of centuries, Gravis only spent time with his family and the Black Magnate. He didn't need to do anything else since he only had to wait for the result.
Master Linus was consuming the fruits at this moment, and he would quickly follow through with everything.
Gravis wasn't afraid that Master Linus would pull back his words. After all, when he became a Heaven's Magnate, he wouldn't even need to invest much time into the things he had promised Gravis.
Master Linus knew the True Law of Matter, which meant that he could create all the different kinds of matter with his Energy. The reason for why that wouldn't have worked had been his Energy, but as a Heaven's Magnate, his Energy reserves would essentially be infinite as long as he wasn't fighting another Heaven's Magnate.
What would stop him from simply creating all the different kinds of things Gravis needed?