Okay, so i cant think of a title for this. Its Sparda sealing away his powers for the sake of mankind and to live as a Human.
Wiki mode!! (not really...)
Sparda was once the Devil's right hand and was born of noble blood. When he was Human, he had a rightous heart but a sudden turn of events led him into Hell. Even there he became an honorable warrior. However, his sense of justice faded along with his humanity as time passed and he began to gain a reputation among his Demon bretheren as the strongest and the noblest.
His loyalty to his bretheren however disppeared when the current Demon Emporer stormed the Human World and took control. Curious as he was, Sparda studied the Humans for it reminded him of his past life. Their emotions, their behavior to the demons' presence and when their together in groups.
Sparda pitied them.
He then rose up against his own world for the sake of the Humans. It took him centuries to bring down the Demon army. During his exploits, Sparda gained the trust of the Humans and befriended a priestess along with her disciples. When they reached the Demon Emporer, the priestess had to give her life to seal the Demon king back into the abyss.
Passed this point in time, Sparda's history isnt really told except the fact that he fell in love with a Human woman during his quiet reign of the Human World. Then after this he just disappeared.
Rumors went around that the New Demon Emporer, Mundus, rose into power in the Demon World and caused a large scale rebellion. Sparda, also fearing that his power was too great, stepped forth and sealed away Mundus along with his own powers.

The amulet was the key to activate his power and the key to finding it on the other side. The amulet was then divided in two for his twin sons to protect.
Wiki off.
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Half of this is hardly canon. This was a quick sketch i did last night when i was off the computer. Im almost done with my current commish. @w@