u/GeXotl

And Imu is the current Earth God. He has dominion over the land, is called "The World" and is the geocentric model the Gorosei revolves around. He also rules on top of the Red Line which is a likely candidate for being the past Hellfire Serpent.

Davy Jones both IRL and in One Piece is seen as a sort of big bad sea demon with a sea depths locker. My take on this is that the locker is a vestige of Jones' former earth power, with which he claims the sea floor.

This would make Blackbeard both an incarnation of the Sea Devil and former Earth God. So his abilities theming would make sense. The Yami Yami is crushing dark water, the Gura Gura can both cause earthquakes and create tsunamis.