Palace of Twilight

The Palace of Twilight is the eighth and penultimate dungeon in Twilight Princess.

Entrance to the Palace
It is located within the Twilight Realm and was originally the home of the Royal Family of the Twilight Realm (including Princess Midna) until Zant usurped the throne from Midna and took control of the Twilight Realm. The palace is accessed once all of the Mirror of Twilight shards are reunited. This location contains the two Sols, which are later infused into the Master Sword.

Themes and Navigation
The first objective is to bring back light to the corrupted Twili people, as well as to bless the Master Sword with said light to turn it into the Light Sword. To reach both goals, Link needs to return two special objects called Sols to the entrance. The Sol is to the Twilight Realm as the sun to the light world: It is vital for life and energy. The two Sols are located on the first floor on the west and east sides of the palace, respectively.

Link will be forced to fight Zant's Phantom twice, once for each Sol. Link will then have to utilize the Sol to activate platforms that lead him back to the dungeon's entrance, all while retrieving the Sol before these mysterious hand-like monsters resembling wallmasters, given the name Zant's Hand, take the Sol back to its resting place. Returning the two Sols to the entrance will infuse the Master Sword with their light, and allow Link to make his way to Zant's throne.

The palace contains a new element exclusive to the palace only: Dark Fog, a haze comprised of shadow crystals created by Zant. They are the pure essence of darkness and shadow, and the element is scattered across various locations of the palace. If Link enters the fog, he will transform into his wolf form, and will be unable to turn back into his human shape until he leaves the fog. Link will be able to cut the dark fog once he has the Light Sword.

In addition to regular monsters seen in the Twilight Realm, Link will also encounter monsters that resemble Zant's mask, thus given the name Zant's Mask, also exclusively found in the Palace of Twilight. They will periodically shoot blasts at Link, then warp to another location. Link will frequently need to defeat these monsters to get keys in the palace.

After a long way to the dungeon's last floor, the throne floor, Link will reach the throne room and battle none other than the Usurper King Zant himself.

Trivia

 * It is presumed that following her return to the Twilight Realm, Midna regains control of the palace and lives out her remaining years there as the ruler of the Twilight Realm.
 * This is one of the only two dungeons (the other being Hyrule Castle) where Ooccoo is absent. The reason is because the previous dungeon, City in the Sky, is her home and she stands there with her son and friends, so she won't be able to help Link anymore for the rest of the game.