PREAMBLE
The saga of the Black Knight begins in the Age of Camelot with Sir Percival of Scandia, distant cousin of Arthur and Mordred. Although his father was a proper follower of Christendom, Percy’s mother still secretly kept to her Druidic faith. When he was young, Percy’s mother brought him before the spirit of Springtime Incarnate, Gwynn. The spirit foretold that Percy had a great destiny ahead as a warrior of peace. Afterwards, Percy’s mother supported his father’s efforts to train him as the greatest swordsman of the age in their remote castle.
After Percy’s parents had passed away, the great wizard Merlin came from Camelot to the lands of Scandia in order to recruit Percy as Arthur’s protector. Arthur allowed his bastard son Mordred in Camelot’s court as his “nephew,” unwilling to acknowledge him as his heir, yet also unwilling to see the evil in Mordred’s heart. Merlin feared for the king’s safety when an inevitable attack came from this blind spot he held for Mordred. Merlin wanted Percy to play the fool, acting as a harmless weakling who avoided physical exertion while secretly protecting Arthur as the masked Black Knight to prevent Mordred from suspecting his true identity and having him killed. In the guise of the Black Knight, Percy saved King Arthur from bandits and was officially knighted as the king declared this mysterious stranger a welcome addition to Camelot.
Once Sir Black Knight was known to Arthur and established as a friend to the Pendragon, Merlin wanted to equip his champion for all that he might face. Merlin acquired a meteorite of unique ore 
called the Starstone, which he and Percy would forge into a talisman for the Black Knight. At a manifestation of the Pool of Blood, the fabled pit along the river Acheron containing the blood of all who had ever lived or died, Sir Percy worked in a blind fever to cast the Starstone into a new shape. Once his workings were cooled by the sacred blood, Percy beheld his handiwork: a sword, a staff, a shield and a chalice, all black as night and possessing the inherent magic of the Starstone. Merlin bade him to choose the item to which his fate would be forever tied and as a knight Percy could only choose the sword.
Merlin made to destroy the other three items, for it was said that the nature of the Starstone’s magic would make the Black Knight invincible so long as he wielded the sword… except to another object forged from the Starstone itself. The staff, chalice and shield were seemingly swept away by the River Acheron. Years would pass as Sir Percy wielded the Ebony Blade against the plotting of Mordred, the Norsemen invaders and other foes of Camelot. He would also prove a frequent foe of Morgan le Fay, Arthur’s faerie half-sister and bitter sorceress. Camelot eventually rotted from within, however, as the falling out between Arthur, Guinevere and Lancelot broke the lines and encouraged Mordred to attack the kingdom directly. The Black Knight arrived to witness King Arthur’s final breath against Mordred’s brigands where he had retreated at Castle Scandia. The Knight killed those who slew the king, but then died himself when a mortally wounded Mordred stabbed him in the back with an Ebony Dagger, forged from the Ebony Staff before Merlin could destroy it. And so fell the Black Knight and the Age of Camelot. [Black Knight (1st series) #1-5, Marvel Super-Heroes (1st series) #17, Marvel Arcana: Black Knight]
Or so the legends say. In truth, Merlin deliberately rose Camelot into the realm of myth and legend after its fall, obscuring many of the literal details of that time period. This would lead to contradictory accounts even from those who experienced Camelot first hand as the legend of Camelot became stronger in reality than the memory. [Black Knight: Curse of the Ebony Blade #4] Contradictory statements claim Sir Percy forged the Ebony Blade or that Merlin forged it alone and gifted it to Percy. Some tales claim the darkness of the blade was a necessary evil, for when the pure sword of goodness Excalibur was forged, the evil extracted from the first sword had to be cast into another. [Black Knight (Digital Comics) one-shot] Indeed, one tale claims eight men tried to wield the Ebony Blade before Sir Percy, only to fall into madness and bloodlust due to the corrupting power of the blade’s magic. With Sir Percy, Merlin finally found a knight of strong will and good heart to fight off the blade’s curse. [New Excalibur #12] Except this was nonsense, since Percy was none of these things. In fact, the blood curse could only unlock the raw power of the blade by feeding on the darkness of the wielder – pure and noble knights failed to wield the blade because, to them, it was just a sword. Merlyn needed an impure and troubled vessel to call upon the blade’s darkness and become Camelot’s dirty but necessary secret as a “berserker in black.” [King in Black: Black Knight #1]
Different stories about Sir Percy also exist. One tale claims he was actually twin brothers named Sir Richard and Sir Percy, who went on a quest for Merlin to acquire the mythical Ebony Blade known as Chaos the Doombringer. The foppish Percy grabbed the sword from its resting place first, wielding a blade for the first time but becoming corrupted by the Ebony Blade’s power. He died fighting Mordred’s men, who mistook him for Richard. Sir Richard then adopted his brother’s name and reputation when he acted as “Sir Percy” in Arthur’s court. [Black Knight (Digital Comics) one-shot] Other tales suggest the Black Knight was not surprised by Mordred’s final treachery but allowed himself to die, either to nobly end the Age of Camelot when its prophesized time was done [Marvel Arcana: Black Knight] or because he was tired of the murderous brutality he carried out as the berserker of Camelot. Sir Percy left an heir, however, and so his son and other descendants would wield the Ebony Blade down through the ages, often trying to do good but always betrayed by the darkness in their own hearts. So long as the bloodline of Arthur and Percy continued and their heirs were touched by madness, the Ebony Blade would retain power. [Black Knight: Curse of the Ebony Blade #1-5]
[Note: The Ebony Blade has also occasionally been misidentified as the Sword of Might of Captain Britain’s lore, such as in Avengers Unplugged #6. This is inaccurate.]