After Nachum ascended, all of Somuli's magic law had been imparted to him by the Lower Realm. Apart from that, his control over Somuli's limited magic energy had increased by leaps and bounds. He could even utilize its mana sources and convert them to magic energies if he wanted. However, he had no plans to do this because he knew where mana originated.
To briefly explain the mana's origin, it was the plane's life force. Beast-likes could utilize it because they possessed beast blood, which could be considered part of Somuli's cycle of life.
Without knowing the full details of Somuli's magic law, others would question how beast-likes were the only ones who could utilize the plane's mana when all complete beings were also inhabitants of Somuli. Why complete beings were not considered part of Somuli's cycle of life would cause a huge ruckus among them if it was ever made public.