Jackie Estacado is a mobster and skilled hitman working for his Uncle Paulie (not a real relative). Jackie was raised in an orphanage after he lost his parents. Jackie had a hard time growing up in the orphanage, though it is where he meets his childhood friend and future girlfriend Jenny.
Jackie was taken in by Paulie and taught the ways of the mob. Uncle Paulie merely needed another Hitman, which is why he decided to take Jackie out of the orphanage and raise him as a mobster. Jackie was an intelligent boy and learned the Mafia's tricks quickly and soon became one of the best mobsters ruling the streets of New York.
He committed various crimes from murdering and drug trafficking to planting bombs. Things continue to go well on Uncle Paulie's side, but the other side of the Chicago family becomes interested in hiring Jackie Estacado and using him as a spy. Eventually Uncle Paulie was informed via Chief Shrote's agent and Paulie decides to eliminate Jackie himself in an attempt to stop the Chicago family from reaching him. On Jackie's 21st birthday he was sent on a fake mission that ended up with Jackie being in a bomb explosion. Luckily it is his 21st birthday, and Jackie survives that accident and joins his previous ancestors in becoming the host to a terrible being, the Darkness. After surviving the attempt on his life Jackie makes Uncle Paulie even more desperate by attacking his drug sources and findng his money hole; as a result his girlfriend Jenny is killed by a crooked cop and partner to Paulie, Chief Shrote. In response, Jackie commits suicide, only to find himself resurrected against his will later on. Later Jackie comes to terms with the fact that he is immortal and can not be killed by normal means .
In Jackie's quest for revenge he travels to hell and back using the powers of the Darkness. This includes demonic minions that Jackie can summon called "darklings", or using the "creeping dark", "dark tentacles", and black holes, all the while finding out about the past of the darkness and trying to maintain his conscious thought and will separate from the Darkness.
Jackie has long dark hair, which almost seems like a part of the dark leather trenchcoat he wears. Contrary to the comics he is shy and doesnt have a sense of humor. In the beginning of the game he is given twin M1911 pistols by his dying friend. He always carries these nickel plated engraved pistols, and these are the only weapons he doesnt throw away.
In the comic books when Jackie uses The Darkness he usually transforms physically, he calls it his armor, and his body, including his face gets covered up in Darkness. This feature is not available in the game, as Starbreeze chose to make things look more realistic in the game, and the armor looked too unrealistic, however, when The Darkness is activated, Jackie's eyes glow, and you can see through mirrors that there is a black hole behind him from which The Darkness spreads.
As Jackie uses his powers he loses control of himself. The Darkness slowly takes over his soul. The player is warned during the game but there are no alternatives, the ending is set and the final kill (Uncle Paulie) marks the loss of Jackie Estacado. The ending cutscene shows Jackie lying on a bench with Jenny, before he has to return to the real world where he's lost.
The Darkness II
Two years after the events of The Darkness, Jackie has become the Don of his own mafia crime family, still feeling intense remorse for not being able to save Jenny and occasionally sees visions of her. Also in those two years, Jackie has been suppressing the Darkness in order to keep his soul. Unfortunately, during a dinner someone puts a hit on Jackie and his crime family and in the ensuing chaos, is gravely wounded. The Darkness calls out to him to release it or die, and Jackie regretfully allows The Darkness to take over. Now Jackie must find answers to who put the hit on him and face a cult that wants the Darkness for themselves, and they'll hurt anyone they have to in order for Jackie to give it to them.