Venom was born as a kittypet, when she was stolen from her mother by her father (after she was weaned, her father wasn’t that cruel!), who was a rogue. While her father was trying to steal her, her mother attacked her father, and her siblings got involved, and, unfortunately, during the fight, her siblings and her mother were killed. After that, she was hardened, and never loved anyone except her father. After a few moons (about 8), she was hunting with her father when a fox jumped into the clearing. Her father attacked it, knowing he would not win, and, with tears streaming down his face, he turned to Venom, and told her, “Run, my beautiful daughter. Run.” After that she was hardened even more, and practiced and practiced fighting to take her mind off of her father’s death until she could practice no longer, and cried. She then was fully hardened, and made a vow to herself to never love anyone ever again, to never again know heartbreak so painful. After around 2 moons, she accidentally wandered into StrikeClan territory, and the leader (who was on the patrol) invited Venom to live in StrikeClan. No one was ever kind to her until Mangosplash, who simply said, “Would you like me to help you gather some moss for your nest?” and she fell. Hard.
All created by my own imagination, but Mangosplash is from @Mango-The-Dog, and StrikeClan is from @Blazewing202, so credit to them!