Once upon a time in the enchanted forest there was an imp named Rumplestiltskin. Imps of course are known to crave human attention. Sometimes they try to get this attention by playing pranks, leaving gifts or playing riddles and rhymes with humans. One of Rumplestiltkin's powers was being able to spin straw into gold. He would often leave strands along the edge of the forest for deserving humans to find. He was especially fond of a lovely young girl named Milah. He would leave trails of gold leading her to the best berry bushes. Over time he came to love this girl and longed to be human so he could be part of her world.
Seeking out the king of the imps Rumplestiltskin asked to be made human. This could be done he was told but would mean losing his powers. He agreed thinking only of his love for Milah. After his transformation he entered the village bringing with him baskets of the best berries and most beautiful flowers. He knew Milah would recognize these as she was the only one he had led to the spot they grew. Soon they were married and had a son whom they named Baelfire. Milah however was not content with the simple life of the village. Greedy and shallow she scorned Rumple's aversion to fighting and called him a coward. Then one day she committed the ultimate betrayal by having an affair with a pirate.
When Rumple confronted her she laughed saying "I never loved you!" Heartbroken Rumple returned home to his son, now the only one left that he loved. When the king begins forcing children to join his army Rumple takes Bael and goes off into the forest. While in hiding he meets an old man who tells him of the dagger which would give him power over the Dark One. Thinking this power would make him able to protect his son Rumple steals the blade and summons the Dark One. In fear of this evil presence he uses the blade to stab the Dark One.
This is when he discovers the truth. The old man was really possessed by the Dark one and by using the blade against him he is released and the spirit of the Dark one enters Rumplestiltskin. As he transforms into the Dark one all of his old powers return as well, giving him unlimited power. Now possessed of great evil and unheard of power he begins his reign of terror. He uses all the bitterness of Milah's betrayal as a shield and loves no one except his son.