Old book series about a young shadow user [duplicate]

Question

About 15-20 years ago I read a book about a young boy / man who lives in a sheltered community. They are protected by some sort of force field and most if not all of them can control some sort of shadow. He does something and gets thrown into a hole to "rot" there by one of the highest members of the community. But thanks to his shadow he manages to escape out of the hole and the communities place (an old fortress?).

He then gets into the surrounding lands and befriends a girl who travels on a ship that travels over land (some sort of pirates or junk gatherers). They hate those shadow users. Still though she helps him.

He then wants to get back to the community to warn them about the plans of their leader (which lead to their destruction / death).

From what I also remember his father was also once thrown into the hole and died there?

That is about all I remember there sadly.

Answer 1

This series is The Seventh Tower by Garth Nix.

The Seventh Tower is a series of six books written by Garth Nix, the result of a joint partnership between Scholastic and LucasFilm. The series follows two children from distinctly different societies in a world blocked from the sun by a magical Veil which leaves the world in complete darkness.

Tal is a Chosen from the Castle, and Milla is an Icecarl from the Ice. Together they discover that an evil, long thought to have vanished, once more threatens their world, slowly and secretly letting its presence be felt. A pact was broken, and a war dormant for two thousand years is rekindling. Danger looms, and it is up to these two children and a small band of unlikely heroes to save their Dark World.

Tal has a "shadowguard", which is a living shadow which can shapeshift and physically interact with the world. The Chosen use Sunstones to wield light magic, and have a color-coded caste system, with Violet at the top and Red at the bottom, with Infrared slaves who are not allowed to use magic.

The story opens with Tal trying to steal a Sunstone, because his father and the family Sunstone have gone missing, and without it they will be demoted soon. He is caught in the act and thrown from the tower. His shadowguard softens is fall, and he lands among the Icecarls, a nomadic, matriarchal society who do not use magic, shun living shadows, and live their lives on the frozen tundras below. But their ship's Sunstone, which they absolutely need to survive is old and failing, so Milla is sent with Tal to get a Sunstone from the castle.