Varian, like many earthlings, grew up hearing the horror stories of the Demon King. A being of unfathomable power, only held back by the Sovereign of Earth, was the nightmare of his childhood.
Sometimes, the horror stories went a bit too far and spoke of a future where the Demon King won. It was a grim future where even the last sparks of hope died out.
It wasn't originally a children's story. It was a cautionary tale for the adults that emerged shortly after the abyssal invasion—warning them of the fragility of their planet, race, and civilization.
Oddly enough, this horror tale that even adults avoided was Varian's favorite childhood tale.
The stark contrast his life gave compared to the grim tale offered made him appreciate the greatness of peace and the duty of people that built that peace, including his father.
His late father and Demon King were the most important reasons Varian turned out the way he did.