^That's a very rushed recap. I suppose it's good enough but a lot of important bits are missing. This was my attempt (from the article about the Belmonts):
This incarnation of the Belmont family was founded by Gabriel Belmont, a knight who belonged to an order called the Brotherhood of Light. He was raised by the order after he was left at their doorstep when he was an infant. Gabriel took the surname of Belmont, after his love of mountains and the high places of the World.
In the year 1047, Gabriel's wife Marie was was brutally murdered by supernatural forces, leaving her soul unable to pass on due to a dark spell. Gabriel is sent by the Brotherhood of Light to the Lake of Oblivion, a place where the living can converse with the deceased. There, his deceased wife, Marie, tells him that the power of the Lords of Shadow, evil overlords who each rule their own domain, can save the world. Their power is derived from a powerful device called the God Mask. Another man from the Brotherhood called Zobek, introduces himself to Gabriel and tells him that, according to a prophecy, a pure-hearted warrior will claim the Lords of Shadow's powers to save the world. The God Mask would also allow Gabriel to bring back Marie.
With the help of Zobek, Gabriel travels to two Lord's domains, defeats them, and manages to retrieve their respective mask pieces. When he finally confronts the final Lord, it turns out Gabriel was manipulated by Zobek in eliminating the other Lords and collecting their mask pieces. With the power of the full God Mask, Zobek would be all powerful. In order to motivate Gabriel to do this task for him, Zobek controlled Gabriel's mind and commanded him to kill Marie. Zobek's actions are revealed to be puppeteered by Satan himself.
After being victorious in a climatic battle with Satan and saving the world, Gabriel uses the God Mask to resurrect Marie. However, the Mask only has the power to see through God's eyes. Marie lied to him so that he would save the world.
Afterwards, through a series of events, Gabriel becomes a vampire in order to save the world yet again, this time from a powerful demon called The Forgotten One. After defeating the monster, he absorbed its powers and unleashes his anger on the world himself. He becomes known as the Dark Lord Dracula and declares war on the Brotherhood of Light, who, according to him, are the reason for his suffering.
XX
Overall pretty lenghty and confusing for a Castlevania game I'd say.