Kingsoul

Kingsoul is a charm in Hollow Knight. It requires 5 notches to equip.

Function
When equipped, the wearer slowly regenerates SOUL.

Upon going to the Abyss with it equipped and completing the dream corresponding to the black orb down there, it will be replaced with the Void Heart permanently. It cannot be obtained again afterwards, as Void Heart replaces it in the slot where it once was.

How to Obtain
Kingsoul is by far one of the hardest charms to get.

First you must go to the Queen's gardens and find a white tree. Talk to the being within to get the first half of the charm.

Then, after the Dream Nail can pierce any mind, go to the edge of the map and strike a suit of armor to enter the White Palace. Complete the area to get the second half of the charm.

After getting both halves, you obtain Kingsoul.