Here below you may read Manly P. Hall on the subject of a “deal with the devil”. Hall describes the way a scenario may play out between a sorcerer and a dark entity.
Hint - the demon wins in the end.
Here are Hall’s own words:
The agreement set forth above is purely ceremonial magic. In the case of black magic, it is the magician and not the demon who must sign the pact. When the black magician binds an elemental to his service, a battle of wits ensues, which the demon eventually wins. With his own blood the magician signs the pact between himself and the demon, for in the arcanum of magic it is declared that "he controls the soul who controls the blood of another." As long as the magician does not fail, the elemental will fulfil to the letter his obligation under the pact, but the demon will try in every possible way to prevent the magician from carrying out his part of the contract. When the conjurer, ensconced within his circle, has evoked the spirit he desires to control and has made known his intention, the spirit will answer somewhat as follows: "I cannot accede to your request nor fulfil it, unless after fifty years you give yourself to me, body and soul, to do with as I may please."
If the magician refuses, other terms will be discussed. The spirit may say: "I will remain in your service as long as on every Friday morning you will go forth upon the public street giving alms in the name of Lucifer. The first time you fail in this you belong to me."
If the magician still refuses, realizing that the demon will make it impossible for him to fulfil his contract, other terms will be discussed, until at last a pact is agreed upon. It may read as follows: "I hereby promise the Great Spirit Lucifuge, Prince of Demons, that each year I will bring unto him a human soul to do with as it may please him, and in return Lucifuge promises to bestow upon me the treasures of the earth and fulfil my every desire for the length of my natural life. If I fail to bring him each year the offering specified above, then my own soul shall be forfeit to him. Signed . . . . . . . . . . . . . " [Invocant signs pact with his own blood.]
While the black magician at the time of signing his pact with the elemental demon maybe fully convinced that he is strong enough to control indefinitely the powers placed at his disposal, he is speedily undeceived. Before many years elapse he must turn all his energies to the problem of self-preservation. A world of horrors to which he has attuned himself by his own covetousness looms nearer every day, until he exists upon the edge of a seething maelstrom, expecting momentarily to be sucked down into its turbid depths. Afraid to die--because he will become the servant of his own demon--the magician commits crime after crime to prolong his wretched earthly existence. Realizing that life is maintained by the aid of a mysterious universal life force which is the common property of all creatures, the black magician often becomes an occult vampire, stealing this energy from others. According to mediæval superstition, black magicians turned themselves into werewolves and roamed the earth at night, attacking defenseless victims for the life force contained in their blood.
Manly P. Hall, The Secret Teachings of all Ages