He convinced the boy his cat had killed his bird and to avenge it by killing the cat, which he did so burying it alive, only to find the bird back in its cage, which he then murdered out of anger.
This was all it took for the tyrant to corrupt the young child’s mind, leading him into a new life as his loyal henchman on Apokolips under a new name that would better reflect his destined occupation.
Despite his monstrous appearance in the Snyder Cut footage, in the comics, DeSaad originally had a more human physical resemblance and, at one time, a humane personality, too, growing up an innocent youth on New Genesis (the essential opposite of Apokolips) until Darkseid used the boy’s pets as pawns in a cruel manipulation tactic.