Some Theories
Is Imu stuck in the holy land because of the treasure of Mary Geoise. He suffering from all the problems of davy jones that robin described. He beat davy jones and is in the same situation as davy jones. That robin described. He can't go past Pangaea castle and the flower room is underwater.
Is Imu making the seraphim to get a new body. Are the pacifista and seraphim Imu has created for a police state or is Imu trying to swap bodies and get around the davy jones contract he is in. He can have a seraphim and pacifista make the contract after swapping bodies. Than order them to suffer the consequences but maybe they're experiments and lack will power. So, he needs to find something else.
In the past people used to dig underground to make refrigerators because of how cool it was. I think the place joyboys hats stored is under the seafloor. Same with potrait of lily. That's why it's so cold.
Also, I think imu might be in nikas body. Gunko fears nika but imu fears joyboy. He looks so similiar to nikas portrait in elbaf. Sometimes, Idk man.
I kind of want imu to be a symbiote or the will of the treasure of Mary Geoise. That looks for omen in people and brings it out. Which is what happened to imu originally.
But it also absolves Imu of the hellscape, He created which hurts the story more. It be cool though.
Also, I think Imu is joyboys Nami or Ussop. I'm calling it.