What a truly riveting story! This was as classic a Hero's Journey as any fanfic I've read, with a literal journey into the underworld to retrieve a prize of great worth, the crossing the threshold, belly of the whale, supernatural aid and meeting with the goddess, atonement with the father, magical flight - the whole package presented in a deeply compelling tale. You've written a fascinating version of that underworld, with an interesting melding of the various cultural mythologies, and your characters are wonderfully 3 dimensional. I felt Harry's grief at the loss of his son, and the grim determination to rescue him. Snape was wonderfully in character, and his time with his father so very moving. Al was a fully realized character, nicely developed, as were your original characters. Nice job!