Godseeker Mode

Godseeker Mode is a game mode in Hollow Knight that is unlocked after completing the first three Pantheons in Godhome: the Pantheon of the Master, the Pantheon of the Artist, and the Pantheon of the Sage. Even though it is unlocked after these Pantheons, it "canonically" occurs after the Pantheon of Hallownest.

The purpose of the game mode is having access to almost all bosses in the game and having most Charms and upgrades unlocked, without needing to play through the main game. Godseeker Mode starts out and takes place entirely in Godhome. There is no way to exit the area.

Features Inventory and Charms
 * The Knight has all Spells and Abilities unlocked except for World Sense.
 * The Dream Nail is not awoken and contains no Essence.
 * A Dreamgate cannot be placed, and warping is impossible.
 * The inventory contains no Items other than the Godtuner and Lumafly Lantern.
 * The Knight has 0 Geo.
 * Almost all Charms are available.
 * Leg Eater's Fragile Charms are all in their Unbreakable forms.
 * Fully upgraded Grimmchild and Void Heart are available instead of  Carefree Melody and Kingsoul.
 * The Knight has all 11 Charm Notches.
 * The Hunter's Journal and Maps tabs do not exist.

Pantheons
 * The first three Pantheons start out unlocked.
 * The Pantheon of the Knight can be entered after completing the first three Pantheons.
 * The cutscene that normally plays at the end of the Pantheon of the Knight after defeating Pure Vessel for the first time does not play.
 * The (non-flower) Embrace the Void ending cutscene does play after completing the Pantheon of Hallownest.
 * After the cutscene, the time spent completing the Pantheon is shown and the Knight wakes up outside the Pantheon.
 * The credits do not play after this cutscene.
 * The Completion percentage is not shown.

Hall of Gods
 * All bosses including Grey Prince Zote are unlocked from the start, with the exception of the Absolute Radiance who needs to be unlocked by encountering her in the Pantheon of Hallownest.
 * The journal entry for Void Idol cannot be accessed since the Hunter's Journal does not exist.

Godseeker
 * The dialogue upon entering Godhome after selecting the game mode is different.
 * There is no dialogue when entering any of the Pantheons for the first time.
 * Godseeker is present in the first three Pantheons and has different dialogue compared to normal gameplay, though that dialogue is the same for all three Pantheons.
 * Godseeker does not appear in the Pantheon of the Knight before fighting Pure Vessel.
 * In the Pantheon of Hallownest, Godseeker only appears in the very first area after defeating Hornet Protector and has the same dialogue as in the other Pantheons. Godseeker is not present in the other locations.
 * After defeating the Absolute Radiance in the Hall of Gods, Godseeker has no dialogue unlike in normal gameplay.

Miscellaneous
 * The Weathered Mask Journal entry that can be acquired in the Land of Storms cannot be accessed since the Hunter's Journal does not exist.

Trivia
 * Team Cherry added Godseeker Mode so that players who wanted to play Godhome could have a distinct save file for it that they could start whenever they wanted.
 * In an early leak, the Godseeker Mode was shown with a different icon. While the select game icon has been changed, this old icon can still be seen when unlocking the new mode.

References

Mode Chercheur de Dieux Modo Buscador de Dioses Tryb Poszukiwacza Bogów Режимы игры