Everyone was waiting for an heir. Shortly after Zira was born, her mother Shetani separately snuck off and had another cub in the seclusion of a desert plane, a male. However, during those difficult kingless times, the ones who were considered most important were the ones who found food. In this case, the lionesses. Shetani wanted to keep it that way, as she was seen as an expert hunter, and quite valued despite her crude and caustic personality. Shortly after birthing the cub she brutally mauled it and tossed it about in her jaws, leaving the lifeless future leader in the sand. Karakal and everyone else was hoping for a male heir, and this was it... Everyone will be disappointed in Zira being the only offspring. Shetani would never be able to tell the truth of what she just did, let alone the reason why. She utterly despised her mate Karakal and did not want him to have another heir that looks like him, sounds like him, smells like him, and learns to be just like him, who would eventually overshadow her and the other lionesses in importance. She justified it in her mind that other lions would kill cubs too... just not their own, and not for these reasons.
She made her way back across a dry plane, and she felt a cold sick feeling course through her, she stopped and saw a dark figure in the corner of her eye, but it was gone when she turned.
She made her way over another rocky dune and froze... at the corner of her eye she distinctly saw the outline of a small cub looking down at her... but it was gone when she turned. Her heart felt like it was in a vice, and she shuddered and forced herself to keep walking. The cub was dead for sure and this couldn't be happening. She began running the closer she got to the then desolate and dry Pridelands. This was her dark secret. She would never tell anyone what happened.
From then on, she was chronically plagued with a chronic recurring nightmare, where she is somehow running or immobile, and the mutilated cub approaches caked in blood, with barely recognizable dripping eyeless sockets, slowly approaching. She could hear him sobbing and asking "whyyy... mother whyyyyy*sob*" and as he draws right next to her, his expression turns from sad to angry, large fangs spurt out, and he rears up and turns into a larger demonic form and lunges. Waking her with a jolt. She was never able to sleep soundly ever again, slowly driving her deeper into an insane private torture.