Gravis immediately started to combine the Laws of Heat and Cold to create the Law of Temperature. Yet, Gravis knew that this Law would take a long time.
When he had tried to learn the level three Law of Elements, he had spent over a century trying to comprehend it. During that time, he had subconsciously learned two other level two Laws. But this Law of Temperature was different.
This Law only required two level two Laws as a prerequisite, not three or more, as was usual. This meant that this Law had a ton of exclusive knowledge inside it. The temperatures between cold and hot didn't have any Laws associated with them, which meant that they were part of the Law of Temperature.
Since there was a lot of exclusive knowledge, it was far harder to learn this Law. After all, the exclusive knowledge didn't have a base Law.
After 20 years, Gravis was still finding a lot of new concepts.