Perseus "Percy" Jackson. Son of the sea god, savior of Olympus, ex-praetor of the 12th Legion. Boyfriend (and hopefully soon-to-be fiancé) of Annabeth Chase, cousin of Thalia Grace, Jason Grace, Nico Di Angelo, and Hazel Levesque, best friend of Grover Underwood.
Betrayed son of the Sea God, Percy is thrown back into Tartarus, and forced to fight all of those he once fought before, along with new enemies, including Tartarus himself, all because of false accusations by some new random demigod.
Supposedly, Percy attacked a son of Athena (he'd never do that to one of Annabeths' siblings, unless he wanted to face the wrath of his girlfriend-- ex-girlfriend now, and her mother) while he was on the way to the Pegasus stalls. He never did, but were there any witnesses? Apparently the nymphs don't count to the gods as witnesses. So after his "hearing" (more of a bashing, if you ask me) he was thrown into lovely little Tartarus. And when they brought him back out so they could read of his 5 adventures and the Quest of the 7... well, let's just say scars last a long time...