The mythological being known for having a dual nature is Janus from Roman mythology. Depicted with two faces, Janus embodies the concepts of beginnings and endings, looking both forward and backward simultaneously. This duality symbolizes transitions, time, and the passage between different states of existence, making Janus an important figure in discussions of change and progress. His complex nature highlights the idea that life is filled with dualities and choices, offering insights into the human experience of navigating through different phases and the necessity of embracing change as part of life's journey.