Black Sword

The Black Sword—less frequently known as the Shade Blade, Blackrock Sword, or B.R. sword—is a two-handed blade the Avatar forges in the Ultima VII expansion, Forge of Virtue. It is one of the most powerful weapons in the series, and the daemon who inhabits it allows it to perform a variety of magical effects.

Description and Abilities
The Avatar forged the Black Sword within the Castle of Fire, after having obtained a blackrock sword blank from the sage Erethian. As blackrock is an unmalleable and hard-to-shape substance, the finished blade was initially unwieldy and cumbersome. To counteract its clumsiness, the hero fused an ether gem—within which the daemon, Arcadion, was bound—to the sword's hilt, imbuing it with the dark entity's personality and power.

Once completed, the Black Sword became bound to the Avatar, and the hero was unable to part with it so long as they tread on Britannian soil. At the Avatar's command, the daemon within was able to deliver instant and swift death to their enemies; to replenish their magical capacity with the life force of the slain; to reign fire down upon the area; or to transport the hero and their companions back to Arcadion's former home on the Isle of Fire. Given the daemon's fickle and often arrogant nature, however, the sword would often fail to slay enemies Arcadion deemed beneath him and, in addition to this, could do little to strike down the undead or creatures born of magic, such as liches and stone harpies.

Forge of Virtue
At the direction of the blind mage Erethian, the Isle of Fire—which had once housed the hellspawn, Exodus—arose from its resting place in the Great Sea around the time of the Avatar's arrival in Ultima VII. Lord British, who had become aware of this momentous occurrence, bade the hero investigate, revealing to them that he had established three great Shrines upon the isle before its initial disappearance, and that trials of Truth, Love, and Courage awaited there for the Avatar to test their mettle. The hero performed admirably in these challenges, but within the Test of Courage, they found themselves barred from victory, for Dracothraxus, the great dragon who guarded the end of the Test, was immortal and required a weapon of unfathomable power not yet forged to slay her. As a gift to the hero for their valor in combat, however, she bequeathed to the Avatar a magical gem, which she had previously stolen from Erethian.

This ether gem was sought after by Arcadion, who had long chafed at Erethian's imprisonment of him within a magical mirror. At the daemon's behest, the hero shattered the mirror's glass with the gem, transferring Arcadion's spirit to the jewel. Chagrined that the ether gem had not given him the freedom he sought, Arcadion resigned himself to being under the Avatar's mastery, seemingly preferring the hero to his former captor. Erethian, not particularly minding the loss, agreed to help the hero obtain the weapon they sought, and produced for them a blackrock sword blank in addition to a magically summoned forge with which to work the blade. While such a sword had long been hypothesized by writers of the era, the Avatar appeared to be the first mortal to make such an artifact reality.

While the hero was eventually able to complete a serviceable sword from Erethian's materials, the weapon was unwieldy and cumbersome, as blackrock made a poor substitute for steel. To balance the blade, and to infuse it with the daemon's power, the hero had Arcadion join himself to the sword, producing a weapon of vast and deadly power. Taking this new artifact back to the trial of Courage, the Avatar slew Dracothraxus at last, releasing her from her immortality and completing the Test of Courage.

Serpent Isle
A year and a half later, the Avatar set sail for Serpent Isle, a cold and distant world where the disrupted lines of power weakened Arcadion's ability to feed, and seemed to loosen the magical ties that bound the hero and the sword together. Shortly after making landfall on the island's shores, the Avatar's company found themselves beset by a strange teleportative storm, which snatched the Black Sword away and replaced it with a piece of ruddy red stone.

After many adventures, the hero was reunited with the sword deep within the hellish prison known as the Mountains of Freedom. Having grown rebellious during their time apart, Arcadion paid little heed to the Avatar's orders. When the hero soon found themselves cornered and at the mercy of the mad mage Lorthondo, the Avatar made the desperate decision to free the daemon from his pact, in return for saving their life from the wizard.

Without Arcadion's presence, the sword became markedly less potent, although the magicks worked upon it would still allow it to function as a vessel for spirits. After the Banes of Chaos escaped and wreaked their havoc upon the realm, the Avatar managed to realign the sword's magic energies using the dead mage Gustacio's Flux Analyzer. With this weapon, the hero went on to slay their possessed friends within the Castle of the White Dragon, channeling the malevolent Banes into the blade and from there into a series of Soul Prisms, from which they could be recombined into the Serpent of Chaos.

It is not known what became of the Black Sword after the Avatar eventually entered the Void on Sunrise Isle, as the hero was snatched from the ether shortly afterward and abruptly deposited by the Guardian's hand on the shores of Pagan, where they found themselves with none of the equipment they had carried with them upon the Serpent Isle. It seems likely that this artifact was either lost within the space of the Void or left upon the steps of the Temple of Balance, and it was never recovered in the hero's future quests before their inevitable ascension.

Trivia

 * The Black Sword may be inspired by a similar weapon known as Stormbringer, which appears in Michael Moorcock's fantasy novels. Stormbringer, like the Black Sword, is a daemon in blade form and its wielder,  Elric of Melniboné, is constantly faced with finding souls it may drink to sate its hunger.
 * Black swords appear in both Ultima Underworld I and  II, but none of them contain similar enchantment to the one that holds Arcadion. Curiously, the Shade Blade, itself, does not appear in Ultima Underworld II, despite the curse that keeps the Avatar from parting with it.
 * In Ultima VII, the Black Sword is capable of killing Lord British, and Arcadion will possess the Avatar as they attack, cackling gleefully at the sovereign's downfall. The sword cannot, however, slay Batlin, and the daemon will claim that "a power greater than his" protects the druid.
 * In Ultima VII, the Black Sword will mock the Avatar should they attempt to kill themselves, the landscape, dead bodies, or inanimate objects.
 * In the usecode for Ultima VIII, there is conversation between the Avatar and Korick about constructing a sword made of blackrock, although it is not possible to discuss this with the blacksmith in the game.
 * Another blackrock sword appears in Ultima IX, although like the black swords of the Underworld series, it carries no daemons.
 * In the EA/BioWare game Dragon Age: Origins, a nod to the Black Sword appears in the form of a tombstone in Haven, with the text, "Questing for Blackrock Sword. Be back soon –MB."