According to Nudd the Chestnut King, the stone that the Blackstar was made from fell from the sky, but it is not clear whether the Blackstar was already of its current size and shape when it fell to the earth or if it was carved out of the stone from the meteor. Regardless of this, his statements imply that the incubi were sealed in the Blackstar after the stone had fallen to the earth and that nobody knows who sealed them.
The Blackstar was lost for ages after it was created. Wizards and sorcerors, both good and evil, continued to exist, but the Blackstar was apparently hidden away and the knowledge of it suppressed, until at last people legitimately forgot about it.
Nimroth found it eventually. He used its power to build the kingdom of Endor and create the undying race. Nudd and three faeren later infiltrated Endor in an attempt to steal the Blackstar, not for evil purposes but simply to deprive Nimroth of his power. They were successful in stealing it but only Nudd survived the ordeal. 
Three centuries later, Nudd gave the Blackstar to Henry York. Henry planned to use the Blackstar to kill Nimiane. Nudd gave it to him on the agreement that he would succeed Nudd as the Chestnut King upon returning to the Second World.
With the help of faeren soldiers and relatives, Henry was able to kill Nimiane by pitching the Blackstar at her like a baseball while she was trying to "drink" him. The Blackstar exploded releasing all of its incubi, but the explosion collapsed in on itself. Nimiane did not die immediately from this, but she was weakened to the extent that she was effectively defeated and was easily killed by Henry later on.
- "That was long ago, before the First World died."—Nudd, p. 381 The Chestnut King hardcover edition.
- The star was a prison to evil, and evil lurked within it, but it was not evil itself.— p. 410 The Chestnut King hardcover edition.
- Brittle leather was packed tight inside, and in that nest there was a single egg [the Blackstar], smooth and round and black as emptiness. Faint white light wavered around its edges like flame.— p. 409 The Chestnut King hardcover edition.
- He [Nudd] slapped [Henry's baseball] through the ash against his palm. "The Blackstar is no bigger than this."— p. 384 The Chestnut King hardcover edition
- And then, gently, he touched the Blackstar. He had expected cold, but nothing like what he felt. The blood in his finger stopped moving, and he felt the skin on its tip begin to harden.
- Pp. 381-383 of The Chestnut King hardcover edition