The White Oak Stake was a very powerful object and the only physical weapon on Earth with the capability to permanently kill an Original vampire. By appearance, it resembles a pale wooden stake. When Esther augmented a stake with the protective magic of the Gilbert Ring, it had metal "veins" enveloping it around from the base.
The stake comes from an ancient White Oak Tree during the time of the genesis of the vampire race. Originally abundant, the last known stake was made indestructible by Esther Mikaelson with the Gilbert Ring so that it could be used indefinitely.
Being the source of the Original vampires' immortality, it was imbued with the power to destroy them permanently when driven through the heart. The process begins, first, by dissection of said Original vampire before both the Original vampire and the stake would burst into violent flames, reducing them to nothing but ash or charred remains. It is possible if the flames were to be expunged before they could consume the body of the Original vampire, then the Original vampire's body can be spared, as seen with Klaus.