In lords of shadow, Dracula starts out as Gabriel Belmont and, after going on a quest to resurrect his dead wife, finds out that, under control from The Lord of the dead, he killed his wife and others and, though he kills the lords of shadow and lucifer (who orchestrated the entire thing to get back at god), he is unable to bring back his wife and the ending essentially sees him break down and plead with her to stay with him. Then, after the credits, it flashes forward to present day and shows that The Lord of the dead, zobek, who spent the entire game deceiving and using Gabriel, is still alive after lucifers attempt to kill him and so is Gabriel, who is nearly a mummy and refers to himself as "dracul" the dragon, the prince of darkness.
Originally, the game was going to end with the dlc that came forth later, but konami had mercury steam cut off the stuff explaining why Gabriel is Dracula and make it dlc. Gabriel, after killing satan, is called by Laura, the former underling of the vampire lord of shadows carmilla, to stop an incredibly powerful demon called the forgotten one. In the process of getting to said demon, Gabriel is forced to drink her blood and become a vampire due to only the tainted being able to entire the shadow realm which holds the forgotten one. Said creature is in the process of trying to escape, putting most of his power into a seal breaker that leaves him weakened, but still strong enough to one shot Gabriel. Gabriel is forced to sneak around and circumvent the forgotten ones attempts and, after the forgotten one puts 99 percent of his power into the seal breaker, Gabriel fights him to a standstill. The seal breaks but, before the forgotten one can regain his immense powers, Gabriel steps in the way and absorbs them himself.
That is how Gabriel became Dracula, a vampire with the power of a being powerful enough to challenge even lucifer.
Gabriel rebelled against the world and god for what he perceived as his unfair fate. He was promised false hope, deceived at every turn, and even betrayed by the wife he loved so dearly. Because, it turns out that before he left Marie to seal another demon, they conceived a child named Trevor Belmont. Trevor would go on to become his fathers equal (back when he was still human) and have a son of his own, Simon Belmont. Trevor would go after his father to avenge his mothers death, but he is not strong enough and gets impaled through the chest with his own weapon. Revealing his heritage to Gabriel, who is shown by the "mirror of fate" that it is true, Gabriel is driven insane with grief and tries to save his son, begging him to stay with him, by using his blood. It, apparently, doesn't succeed and Gabriel entombed Trevor, but not knowing his name, calls him "alucard".
Years later, Simon goes to the castle, recovers Trevor's weapon (a copy of the combat cross, the vampire killer that Gabriel used and destroyed after killing the forgotten one) and confronts Gabriel. He is not alone though, for, though it took some time, Trevor is resurrected as a vampire and takes the name "alucard" . Together, alucard and Simon defeat Gabriel (Dracula), but it doesn't stick due to needing the entire combat cross, Simon escapes, alucard goes back to the mirror of fete and gets the stake that Gabriel broke off his vampire killer when killing carmilla, and then he escapes in bat form as the castle crumbles.
Alucard thinks the stake will work, but later, after 50'years and a failed siege by the brotherhood of light, alucard defeats Gabriel but again, only puts him to sleep. Not wishing to fight his son, Gabriel, upon coming back again, stops his wrath on humanity and secluded himself, becoming the mummy Dracula we see in the first games epilogue sequence. And that is where we continue from in the beginning of lords of shadow 2.
And before you ask, this is a new continuity and may likely stick around due to it bringing castlevania back to the mainstream. Konami is likely to continue the lords of shadow sub series, even without mercury steam.
So, in essence, Gabriel has been forced to kill his wife, friends, and, even after accomplishing his initial task, is unable to bring her back. He then is forced to become a vampire to save the world, which essentially stops him from ever hoping to join Marie in heaven, especially having absorbed the forgotten ones powers. Then, later after snapping at gods children, humanity, he unknowingly kills his own son and only finds out just as Trevor dies. Then, for centuries, blood is forced to fight blood and, in the end, he is forced into seclusion. Unable to live, yet unable to die.
Gabriel Belmont is the best Byronic hero we have in gaming right now, at least in my view, even if the story of the lords of shadow isn't as spectacular as the legacy of kain or silent hill.
Any questions?