The jar of ashes is a small item that can be found in Hellfire Peninsula.[45.0, 87.2]
Here is a jar of ashes. These are the ashes of my sanity, my passion, and my drive. All, utterly destroyed by themselves. May all those who look upon these desolated lands of Hellfire remember this fallen peon. He shed blood for the Alliance, and sacrificed for the Horde only to be driven utterly mad by the wicked and soulless ones who devoured what he held most dear. As they feast from his toils, may they suffer his wrath. Maybe not in this world, but in every world hereafter. It is my declaration, my solem oath, and my everlasting promise. I will avenge my suffering.