Beast Control: Why Can I Only Contract Buildings?

As a young man in the 21st century, Luo Yu said that he had traveled through time, and he still wanted to control the world of beasts, angels, demons, and dragons. Luo Yu said that he wanted them all. In the awakening ceremony, what is a contract-only building? What does it mean to be a natal beast? It requires materials to be born. The same world view of beast control, different beast control, let's see how Luo Yu uses his unique talent to subvert the world. (No heroine yet, not a harem story)