The story of Daniel's abiding faith, even when cast into the lions' den, is told in the Book of Daniel in the Jewish scriptures.
In addition to stories of Daniel's trials at the Persian court, the book features symbolic imagery of fantastic animals, world-wide cataclysms, and the ending and beginning of epochs. It set the pattern for the Christian Book of Revelations, and scholars of both faiths continue to debate its ultimate meaning.
There is some scholarly support for the theory that Daniel was a mythic character, pre-dating even ancient Biblical writings. As we might anticipate given the meaning of his name, these early myths portray Daniel as a judge with a high reputation for wisdom and piety.