One does not simply ask Fallenreaper if Fallenreaper is writing a novel. G.R.R Martins everywhere!- beware
Demigods, as a rule, cannot bend space-time and create personal planes or travel between dimensions of their own power. A god may, however, move them between dimensions or planes of existence. Thus, should a god wish to banish a demigod to another plane the demigod would be utterly helpless.