The Black Elfstone is a large black gemstone, combining all the elements of three normal Elfstones (heart, mind, and body) into one talisman. The Black Elfstone is a powerful magic that nothing can stand against, for it has the power to negate other magics. However, there is a price to be paid, as any magic that is negated is then transferred into the holder of the stone, changing and remaking that person.
Its ability to negate any magic meant that the Black Elfstone can be used as a potent weapon. During the Second War of the Races, the Druid Bremen understood the incredible destructive potential that the stone held and what that would mean if it fell into the hands of the Warlock Lord. He asked the Elven Druid Tay Trefenwyd to embark on a quest to the Breakline and find the Elfstone in the ancient fortress of Chew Magna, where it had been hidden since the Age of Faerie.
Tay Trefenwyd traveled to the Breakline with a small company organized by his best friend Jerle Shannara go after the Elfstone, one that included Jerle and the tracker Preia Starle. Inside the fortress, Tay used his Druid magic to become one with the spirits protecting the stone in order to safely retrieve it, and when he had recovered the stone the fortress began to crumble. The surviving members of the group fled as the castle turned to dust around them.
Once they escaped the fortress, the company was confronted by a massive force of Gnomes and a pair of Skull Bearers, all under the Warlock Lord's command. Caught with no other choice left to him, Tay used the Black Elfstone on the enemy, obliterating them all within seconds. but inflicting terrible damage on himself as the magic of the Skull Bearers was transferred into him and began converting him into a creature of evil. Realizing what was happening, Tay used his magic to draw all the air out of his lungs and end his life before he was completely converted.
Jerle Shannara returned to Arborlon with the Elfstone, hiding it until Bremen's return. Jerle then gave the Elfstone to Bremen, who in turn gave it to Allanon before he died as a means to seal and unseal Paranor, the Druid's Keep. At some point, Allanon hid the stone in the Hall of Kings.
The Stone King Uhl Belk later stole it from the Hall of Kings, replacing it with an Asphinx to kill anyone who might come searching for the stone. After Uhl Belk had turned Eldwist to stone he created an elemental, a son called the Maw Grint, to travel out of Eldwist and turn outlying lands to stone. Uhl Belk repeatedly modified the Maw Grint with magic to make it more efficient at its task, but in doing so he turned his son into a monster that threatened to kill him as well. He took the black Elfstone so that he could use the Elfstone's magic to keep the Maw Grint in check.
However, use of the stone to negate the Maw Grint's magic only meant that Uhl Belk himself started turning to stone, and he eventually ended up fusing himself to the stone floor inside a massive dome at Eldwist's center.
The King of the Silver River recognized the threat Uhl Belk posed and created a child of his own to send to Eldwist, an elemental named Quickening. She was tasked with restoring Eldwist and the land around it back to its normal state, but that task could only be accomplished if the black Elfstone was taken away from Uhl Belk, as the Elfstone's magic would be able to negate her own with ease.
Quickening was told by her father to seek out Walker Boh, Morgan Leah, and Pe Ell to help her in her quest. Walker in particular had reasons of his own to take the black Elfstone out of Uhl Belk's hands, as it was the only magic available that would be able to restore Paranor to the Four Lands.
After discovering Uhl Belk's location and urging him unsuccessfully to give up the Black Elfstone, Quickening, Walker, and Morgan returned to the Stone King's dome and launched a surprise attack. When Morgan stabbed Uhl Belk in the arm with the broken Sword of Leah, the creature dropped the Elfstone and it was retrieved by Walker. The trio fled as the Maw Grint, sensing that Uhl Belk had lost the Elfstone, returned to confront its father.
After traveling back to the place where Paranor once stood, Walker used the Elfstone to make the lost Druid's Keep reappear and gain entry. Inside, he discovers Cogline and Rumor waiting, as they had been since the volume of the Druid Histories Cogline had been holding had burst into flame and transported them there. Walker also learns that his quest is incomplete, in that Paranor is not yet fully restored but is stuck in a half-real, limbo state, and that he has not yet become a Druid.
After days spent studying the Druid Histories, Walker comes to the conclusion that he must use the Black Elfstone again, this time on the mists that guard the Keep. Once he does so, the magic of the mist is transferred into him by the Elfstone, and he discovers that the mist is the spirit of Allanon and of all the Druids gone before, including all their knowledge, memories, and emotions. This absorption of the magic remakes Walker Boh into a Druid, even changing his physical features so that he resembles Allanon somewhat. The absorption also completes the process of bringing Paranor back into the physical world.
After fulfilling his task to restore Paranor and the Druids, Walker placed the black Elfstone deep in a vault within Paranor, where it remains.
Unlike the blue Elfstones, the black Elfstone does not seem to need a sufficient amount of Elven blood to be used, nor does it need to be freely given. Despite Walker Boh's Elven blood being extremely thin, he uses the Elfstone with ease, with none of the problems Wil Ohmsford experienced with the stones. He is also able to use the Elfstone despite having taken it from Uhl Belk without the Stone King's consent.