The Champion of Olympus (HP and PJO/HoO crossover)

Welp, time to change everything. This used to be Voldemort's Grandson, but I decided that was too overused. All of Percy's friends were killed in the Giant war. He comes out of it completely different, as the Champion of Olympus, Prince of the Sea, and... An Olympian. The Fates must really hate him. With new forms and powers, Percy struggles to understand himself. Meanwhile, his mother is revealed to be a wizard, and Percy gains a new job at Hogwarts, teaching a new class. When old enemies arise, will Percy be able to work together with Harry, or will good finally overtake evil? And will Percy be able to grasp his newfound power, in time to save the world- again? (Takes place during Half-Blood Prince)

(Leo never met Calypso. Percy fell into Tartarus alone (Will explain somewhere in the book, or I'll write another book))

(PROPHECY OF SEVEN - MY VERSION)
Seven half-bloods shall answer the call
To hurricane the world must fall
Sacrifice, unless the earth shall win
And the last hero broken within