The song "Mystery" by U.D.O. explores themes of darkness, inner struggles, and the complexity of life. The lyrics depict the multifaceted nature of existence, alternating between contrasting elements such as redemption and death, kindness and cruelty, victimhood and disease. The narrator identifies themselves as a force to be reckoned with, embodying qualities that both harm and manipulate others. The song suggests that the narrator has attempted to possess virtuous qualities, to be kind, but ultimately failed and revealed their true nature as someone who is not nice. They are portrayed as a metaphorical cancer, injecting themselves into the lives of others and infecting their blood with their negative influence. The lyrics also imply that the narrator is a dark shadow, a representation of the past, and a trashy figure. The chorus proclaims the "mystery of life," which touches the listener at a deep level and screams out in pain. It suggests that life can be a tormenting experience, where one's soul is ripped apart and can transform into a bad beast. The repetition of the phrase "bad beast" reinforces the idea of the complex and dark nature of humanity. Overall, "Mystery" delves into the enigmatic and often tumultuous aspects of life. It highlights the inner struggles and the duality of human nature, combining both light and darkness, good and evil. The song invites listeners to contemplate the complexity of life and the challenges one must face when confronted with their own inner demons.