To believe in legends, one needs to accept there are powers and beings capable of things beyond the human imagination. God, who created all, gave distinct abilities to all entities, such as angels, gods, humans, creatures, and mixtures of each. They lived as one, some mortal, some immortal.
Many millennia ago, humans began to worship immortals, making them more significant than they were meant to be. For that reason, they were no longer able to live as one. Mortals always wanted what the immortals had, and the immortals used them as their minions to wage and fight in wars, not their own. God became disgusted and separated them all into separate realms. Immortals could no longer live with humans but were still tasked to watch over them when called upon, with consequences if rules were broken.
Unfortunately, if a human and an immortal were together longer than necessary, the mortal would become confused and wonder if they are experiencing reality or fantasy, dreaming or awake. This otherworldly confusion often led to insanity and sometimes death.
What happens when immortals become obsessed? When their obsession is a mortal?