The soulshredding songs of damnation first sung by the Witch Kings
As a powerful form of sonic energy, Blacksong has no physical characteristics, on the few occasions where it can be seen, it appears as translucent black waves of vile darkness.
Physical & Chemical Properties
Blacksong has no physical nor chemical properties that are known - it is most commonly heard rather than felt, but on the rare occasions in which it is infused into a weapon it is so potently loud that it vibrates on a speed and frequency that invokes a cascading, apocalyptic resonance in whatever material it touches as it matches its harmonic destruction frequency and literally rattles its component molecules apart - leading to the source of the 'melting' effect on materials who are touched by something infused with Blacksong or who hear it for extended periods of time. Blacksong is also said to transform those it slays into horrid Dread Wraiths, enslaved to The Witch Kings of Bhorsis-Razghûl and their Six Black Thrones, their souls perpetually torn from the cycle of souls and bound to the same eternal punishment as their new Witch-King Masters.
Geology & Geography
Blacksong does not occur naturally - it can only be found in spots where its insidious masters, The Witch Kings of Bhorsis-Razghûl, hold power or held it in ages past - most commonly vibrating off the Blackstone steles or pillars places in areas they once controlled. In very rare circumstances, in places of especially vile power where those Witch Kings were especially powerful, the wind itself can moan with Blacksong energy - as is the case with the swamps of Bhorsis-Razghûl, where the phrase "The Black Winds Moans" is a common warning to those seeking to enter the swamp, lest their souls and bodies be taken by the destructive power of the blacksong.
Origin & Source
The Blacksong originated from The Witch Kings of Bhorsis-Razghûl - it was invented by the damnable Witch-Kings in their neverending plot to bring ruin to The Spirit King as one of their greatest weapons. It is synonymous with their language, Blackspeech, source of all Bardic Magic - and though it is naturally what results from speaking that insidious tongue(though much less potently than normal), it can also be seperated out into raw elemental sonic energy to be infused into weapons or armor or spells.
History & Usage
See The Witch Kings of Bhorsis-Razghûl for more info on the history of the creators of Blacksong. As for the material itself it has little history - few dare to wield it since its inception, so little to no history exists.
Blacksong was discovered and invented by The Witch Kings of Bhorsis-Razghûl.
Blacksong is commonly used by none save The Witch Kings of Bhorsis-Razghûl and their servants, or the especially desperate.
Trade & Market
No sane vendors will sell Blacksong - to do so is to risk damnation and destruction of one's eternal soul.
Blacksong cannot be 'stored' normally - it is infused or carried within one's soul. If some means exist to store and harvest it, they are not widely known.
Elemental / Molecular
None, but those who hear it universally claim to smell freshly cut grass.
None, but those who hear it universally claim to taste blood and hear sobbing from nearby.