Deku Tree Chasm
Tears of the Kingdom
The Deku Tree Chasm is located at the back of the Great Deku Tree's Navel, within the Great Deku Tree himself. It leads to a sealed-off area of Korok Grove, where a Gloom Spawn exists. Link must enter it to defeat the Gloom Spawn and ensuing Phantom Ganon in order to free the Deku Tree and Koroks within Korok Forest from the gloom keeping them all frozen, and the Lost Woods completely impassable.
Until the Phantom Ganon is defeated, the only way to access the Deku Tree Chasm is by entering the Depths from another Chasm, travelling through Korok Grove and ascending to Korok Forest through the column near Rikonasum Lightroot.