Seventeen-year-old Haithem knows the warnings; use the stone and risk corrupting your soul -its too bad Haithem needs its magic to fulfill his destiny.
The wording here is awkward--you've put a second person "you" in the middle of what should be in third-person, and I think the same idea can be stated more directly.
Seventeen-year-old Haithem knows that using the stone might corrupt his soul. It's too bad Haithem needs its magic to fulfill his destiny.
Haithem never fit in with his quiet rural community, so although he was shocked by the news that he was a member of an ancient magic-wielding race, he knew it to be the truth. He was awarded his birthright - a strange green gem, said to be imbued with the power to change its keeper's destiny. But is the stone a blessing or a curse?
This also seems a bit awkward, and I don't recommend rhetorical questions in queries--some agents have a real pet peeve about them.
When (character) awards Haithem a strange green gem--his birthright as a member of the (race name), an ancient magic-wielding race--he warns him that the stone is imbued with the power to change its keeper's destiny. That may be a blessing--or a curse.
Haithem sets out on a perilous journey to find his kin and request their aid against Gorthok, the Evil King of Suendra. He is not aware that Gorthok hunts the stone he carries until Gorthok sends his depraved wizards and barbarian soldiers to wreak havoc on the countryside and its peaceful inhabitants.
Avoid clichés like "perilous journey" and "wreak havok." This seems backwards to me--please let me know if I've misunderstood. When Gorthok, the Evil King of Suendra, sends wizards and soldiers to destroy Haithem's community and find the stone, Haithem sets out to find his kin and request their aid against him.
With the aid of companions he meets along the way, including a young rogue fighter, a beautiful warrior woman, and an ancient magical beast, Haithem finds that the story of the stone runs deeper than he could possibly have imagined. Now he must risk everything - including his soul - to save the land and the people that he loves. He hopes it will be enough. This part reads more smoothly, although the characters sound a bit cliché (please tell me they don't meet in a tavern...). Try to find a way to describe them that makes them more vibrant, memorable, and unique.
DESTINY STONE is a 104, 000 Young Adult fantasy. It is a standalone with series potential. Thank you for taking the time to consider representing my work.