Starsteel

Properties
Starsteel appears like any other metal. It is greyish, hard, although naturally shiny. What separates it from earthly metals, however, is that it is indestructible by normal means. It cannot be crushed by sea pressure, broken into shards, or melted into slag. No matter what the World Government has tried to do with it, it has continued to gleam.

The darker side of the metal involves two other properties: Starsteel will pull itself towards nearby Starsteel, and it can contain souls. Any human it slays has their souls sealed into the metal. And once the energy from each soul reaches 10,000, it can grant any wish within its power. For example, when Chalice wished to become the strongest human on the planet, it sent all the soul energy it contained into her body, enhancing all her physical stats.

History
The first known mention of Starsteel was approximately 22 years ago, by the Marines. They recovered it on an island on the Grandline and tested it, discovering the physical attributes above.

Around 5 years ago, a rising rookie pirate named Chalice recovered a hidden deposit of Starsteel. The smith Donovan crafted it into a foil for Chalice's first mate, Charles Gracepoint. It was named the Vague Katti and never dulled.

Then 3 years ago, Chalice raided Marineford and recovered the Marines' Starsteel with the Vague Katti by using their natural attraction. She brought the two blades back to Donovan and had them forged into a proper sword: the Aspire.

Using her alliance with Adas to attract pirates, she slaughtered them all to begin powering up her sword. After roaming the seas for a few weeks, she managed to acquire the necessary energy. She then attacked Marineford one last time, nearly destroying it. Chalice was slain by the Aspire when Charles managed to flick the sword away from her and strike her down with it.

Since her soul held the 10,000 units necessary for a wish, she sealed herself in the sword to make her wish - "Save Charles." Bound by the will of the Starsteel, The King revealed Himself and sent her body, the Aspire, and Charles away to Enderedge Island.

And to this day, it sits on the legendary swordsman's grave.