Pale Ore is an item in the game that is used a currency for the Nailsmith, located in the City of Tears. He will upgrade your weapon up to 4 times using Pale Ore and Geo.

Weapon Upgrades are as thus:

STARTING NAIL: Free - Old Nail[vignette.wikia.nocookie.net], 5 DMG
UPGRADE I: 250 Geo, 0 Pale Ore - Sharpened Nail[vignette.wikia.nocookie.net], 9 DMG
UPGRADE II: 800 Geo, 1 Pale Ore - Channelled Nail[vignette.wikia.nocookie.net], 13 DMG
UPGRADE III: 2000 Geo, 2 Pale Ore - Coiled Nail[vignette.wikia.nocookie.net], 17 DMG
UPGRADE IV: 4000 Geo, 3 Pale Ore - Pure Nail[vignette.wikia.nocookie.net], 21 DMG

PALE ORE I

To find this Pale Ore, you must unlock the Ancient Basin area. This area is underneath the Royal Waterways and can be unlocked with the Tram Pass.

When first arriving to the Ancient Basin, go to the left of the Tram Station where Cloth is. Underneath Cloth, there is a small area with a lot of Mawleks. Defeating the two Lesser Mawleks guarding an item gives you the Pale Ore.

PALE ORE II

This Pale Ore is given as a reward by The Seer, the moth that gives you the Dream Nail in the Resting Grounds. Once you have collected 300 Essence with the Dream Nail, The Seer will give you this Pale Ore.

You can find Essence all throughout the kingdom, most notably via defeating Dream Warriors or collecting it from Whispering Roots.

PALE ORE III

To find this Pale Ore, you must have already unlocked the Crystal Peaks area. This area can be found to the east of the Forgotten Crossroads and requires the Desolate Dive ability to access.

Once Crystal Peaks has been unlocked, you must travel to the highest point of Crystal Peak using the Mantis Claw ability found in the Mantis Village in the Fungal Wastes. The Monarch Wings are recommended but not required for this. You can find them by defeating the Broken Vessel in the Ancient Basin. The highest peak of the area is Hallownest's Crown, where you will find a statue containing a Pale Ore.

PALE ORE IV

This Pale Ore is found in the deepest room located in Deepnest. Deepnest can be unlocked via defeating the Mantis Lords in Mantis Village in the Fungal Wastes. To access this area's Pale Ore, however, you must defeat Nosk. You must also have the Monarch Wings and Mothwing Cloak, which can be found by defeating the Broken Vessel and Hornet 1 respectively. From the area's Hot Spring, travel left and make a precise Double Jump + Dash to break a wall in the left of the room. Upon entering, break another wall on the left and follow your mimic all the way to Nosk's Room. Defeat Nosk, then proceed right to claim your Pale Ore.

PALE ORE V

This Pale Ore is given as a reward by the Grubfather in the Forgotten Crossroads. Upon rescuing 31 Grubs scattered all across Hallownest in jars, the Grubfather will reward you with a Pale Ore.

This task can be significantly easier with the Collector's Map, an item which plots all unrescued Grubs on your map. You can find this item by defeating The Collector in the Tower of Love in the City of Tears.

PALE ORE VI

This Pale Ore is given as a reward by completing the Trial of the Conqueror in the Colosseum of Fools, the second Trial. You must complete the first Trial, the Trial of the Warrior, beforehand.

The Colosseum of Fools is located in Kingdom's Edge, east of the City of Tears.