The Cobalt Wars took place 7 millennia ago, during the Masa'u Era. The two main sources are Yusi Mase'p's 41 or so volume Cobalt Wars and the 21 or so volume Chronicle of the Cobalt Wars.
The Cobalt Wars – Volume 1[]
By Yusi Mase'p
The War between the two Brother Kings, Gomi'r and Samet, had already lasted for nearly 20 cycles and neither had been able to gain a decisive advantage. Their armies did battle in a maelstrom of blood and fury and their hatred of each other had not diminished in any way. Samet was a powerful sorceror. When an ancient parchment found not far from a battlefield was brought to him he locked himself into his apartments for three days. When he emerged he roared like a demented man that his new ally would enable him to win the war. He had just opened up a pathway to Hell.
In those days a rumor arose from the limits of the Masa'u empire. Hordes of demons appeared everywhere and out of nowhere in indescribable fury. Gomi'r's legions were soon reduced to nothing. But the demons did not stop there. Next they attacked Samet's armies. Astaroth, the Prince of Demons, took over his palace and ate the head of the Brother King.
The Cobalt Wars – Volume 2[]
By Yusi Mase’p
The humans assembled all their forces under the banner of a great hero, Kushulainn. Leading his legions he did combat with the demons in order to prevent them from taking control of Phaënon. Thus began the Cobalt Wars.
Words cannot describe the horror of the following cycles. The dead were numbered in the millions and on more than one occasion the fate of the human race depended on the outcome of a battle.
Fortunately Kushulainn never defaulted in his courage and daring. Cycle after cycle he won back territories from the infernal armies.
The Cobalt Wars – Volume 41[]
By Yusi Mase’p
Fate took a turn at the battle of Amiza. Leading the human armies, Kushulainn decimated the infernal legions. All the lifelong day he sundered incubi and succubi, shedding their blood on the soil of Phaënon. When the battle was at its most intense he flung himself at Astaroth and engaged him in single combat.
Their duel lasted seven days and seven nights. On the morning of the eighth day the humans finally dared approach. Astaroth lay inanimate on the ground. But Kushulainn had disappeared. They cried out, searched the ruins and the surrounding forests, but to no avail.
In great haste they built a cage of epyfandre and shut Astaroth inside it. Then they cast the cage into a lake of boiling lava. The gilded prison slowly sank into the entrails of the earth.
No one ever saw Kushulainn again, or learned what had become of him.
Chronicle of the Cobalt Wars - Volume 21: Astaroth, the Prince of Shadows[]
In the ninth year of the Cobalt Wars the hordes of Astaroth’s demons covered the surface of the earth. The human armies led by Kushulainn began to give way under the terrible assault of the demons. The war was heading towards a deadly outcome for the humans. The more demons they killed, the more appeared. They had to find a way to kill Astaroth.
Kushulainn assembled all the sorcerors of Phaënon. They thought for forty days before they found a means of definitively destroying Astaroth. The decision was kept a secret. No one ever knew anything about it.
After the final confrontation between Kushulainn and Astaroth all the sorcerors of Phaënon, as well as the hero Kushulainn, disappeared for all time. Their terrible secret disappeared with them.
The mystery of the weapon capable of killing Astaroth was recounted in only one book, the Book of Nout, by the renegade sorceror Matanboukous.