Let me tell you the story of Poisondrank.
The Sensitive Midnight of The Deceiver of Kingdoms settled the Dark Fortress of Poisondrank in the year 70. Except for a pair of hydra attacks and the usual random murders, Poisondrank had peace for 28 years - until in 98 The Crimson Season, an elven group, attacked it in force with giant war beasts. For 3 years straight they attacked, pillaged, and withdrew, each time taking heavy losses themselves at the hands of the fortress's demonic masters. Then, in the invasion of 101, the elves found more than they had bargained for: the copper monster Sasmcith Cystlust the Putrid Lice, the only one of his kind: a gigantic skink twisted into humanoid form, with lidless eyes; jagged and close-set copper scales; an emaciated appearance; and the ability to shoot webbing. After the last of the goblins was defeated, he strode onto the battlefield and won the day for Poisondrank. In the face of such a foe, the Crimson Season extended an offer of peace which Sasmcith accepted.
The master was called in the next season to defend another holding of The Deceiver of Kingdoms, leaving its remaining citizens behind in the nearly-abandoned fortress. They were three human children, second-generation abductees: a ten-year-old boy named Azstrog Badpull; a four-year-old boy named Zolak Wickedflinched; and a three-year-old girl named Asno Horroreerie.
When Azstrog reached adulthood in 103, he became a babysnatcher. Over the course of 30 years he abducted as many children from thirteen nearby human and elven settlements - until at last the man who had been his tenth abductee murdered him in cold blood. Ah, sweet irony.
And this is how Poisondrank became an entirely human and elven Dark Fortress while still a member of the goblin civilization The Deceiver of Kingdoms.