Anethron was Kol Thezar's Replacement.
The Third Invasion
When Kol Thezar was killed and the demon gate destroyed, The Black Demon's rage knew no bounds. He'd lost every grip he had on Derear. He promoted Anethron to the rank of cheif dreadlord and gave him orders to invade Derear.
Anethron corrupted human wizards, who would eventualy become Lichs, to build Dark Portals in The Mountains. Anethron sent demons through to reinforce the Lichs ranks. When they were ready the Lichs would launch an undead invasion of Belemondo.
The undead legions preformed well in the opening stages of the invasion but the attacks slowed down when their number became to great.Also human tacticians realised they had to attack the figure at the top.
A month after the undead invasion began all the lichs had been killed.
Also, Dwarf explorers found the Dark Portal and destroyed it.
Anethron was killed by the Black Demon for his failure.