It's not for everyone, just a select few. A select few born under Mercury's retrograde were born differently. A curse or gift placed upon them. Gifts or curses that are associated with that person's personality type.
Aina Hallow lost her mom at age eight and was forced to live with her scum uncle. Aina was highly suicidal, and when the time came to end her life, everything changed. She could no longer seem to die. Because of a Suicide attempt gone wrong, she got involved with a group of misfits led by Ulf Thatcher. He's aggressive, rude, and doesn't seem to trust her. Despite hating him, Aina feels compelled to help. She learns so much more of what's inside her, being human and being a retrograder, and gains a feeling of desire. With her and Ulf's mutual hatred, will they fight each other, or work together to fight the enemy? Maybe both.
With the friends she gains, he power grows and they plan to win this fight.