Imu is the Earth Deity and stands for matter/order/ rationality
Nika is the Sun Deity and stands for soul/freedom/dreams and love
The Rain Deity is a servant of the Sun Deity (Dragon?) because both are in the sky and represent the heavenly
The Forest Deity is the servant of the Earth Deity and represent the opposite
They’re like heaven and earth, ying and yang
The Sea Deity is the middle ground, water can be found in earth and plants but it also reflects the sky
Imu is also the troubled shadow and listens to the fragmented moon -> Garling?
edit: Mihawk has also a connection to the serpent. I mean his name is Dracule