Mephistopheles: I am the Spirit that denies! And rightly too; for all that doth begin Should rightly to destruction run; 'Twere better then that nothing were begun. Thus everything that you call Sin, Destruction- in a word, as Evil represent- That is my own, real element.
(Johann) Wolfgang von Goethe - Faust (posth. 1832).

The devil, in the form of Mephistopheles, wagers with God that he can tempt the good Dr. Faust, if allowed to spend a little time with him. Faust's despair of the futility of his scholarly pursuits to free him from the restrictions of earthly life drives him to the brink of suicide, but he is unable to complete the final step. Mephistopheles duly appears as a small black stray dog, which Faust takes a liking to, beliving it to be more than it appears. The dog duly transforms into Mephistopheles, and proposes to offer Faust everything he desires, if Faust would only be his servant thereafter. Faust agrees, but sets a condition to the bargain that Mephistopheles may only take him if he is truly content with the world, and all things in it. A deal is struck. Mephistopheles keeps his end of the bargain, waiting for his opportunity to capture the soul of the Doctor, until finally - in his twighlight years - Faust is responsible for the death of an elderly couple and Faust is again contronted by the futility of his efforts in life, and laments his lack of personal freedom, even with the help of magic.

At the moment of Faust's death, Mephistopheles gathers his devils together to capture the Doctor's soul as it leaves his body, but a band of Angels arrives. Distracted by the beauty of the Angels, Mephistopheles misses his chance and Faust's soul escapes, to be carried off by the Angels, and reunited with his lost love.