Pale Ore

Pale Ore is a material used in the creation of high-quality weapons. Providing the Nailsmith with Pale Ore will allow him to upgrade the Hollow Knight's nail. The first upgrade requires no Pale Ore, the second requires one, the third requires two, and the final upgrade requires three Pale Ore, for a total of six.

Locations
There are six pieces of Pale Ore to be found in total. Three of them are found on the ground in various locations: Three more are given as rewards for accomplishing various tasks:
 * In a sub-location of the Ancient Basin, found to the left of the tram station and the main Ancient Basin entrance. The place is infested with Lesser Mawlek, who are tough enemies to fight, so come prepared. Two Lesser Mawleks guard the room with the Pale Ore, and you will have to beat them simultaneously.
 * Embedded in a statue at the very top of the Crystal Peak, known as Hallownest's Crown. Normally can only be reached with the Monarch Wings.
 * In a secret spot in the Deepnest, accessed by breaking a wall in the room just left of the hot springs. It is guarded by the deadly shapeshifter Nosk.
 * Given by the Seer in the Resting Grounds after collecting 300 essence for the Dream Nail.
 * Given by Papa Grub for rescuing a certain amount of Grubs (exact amount unknown, but significantly over half).
 * Given as a reward for completing the second challenge (Trial of the Conqueror) in the Colosseum of Fools.

Bugs

 * Due to a known glitch, the Colosseum of Fools does not yield the correct rewards in the GOG version of the game, making the last Pale Ore unobtainable and the Pure Nail unavailable.