Chaos decks deliberately make games less predictable through random outcomes, unusual replacement effects, and cards that scramble otherwise orderly game states. The goal is usually to make every turn difficult to anticipate rather than follow a rigid, linear plan.
If looking for chaotic gameplay, Possibility Storm replaces cast spells with unexpected ones while Grip of Chaos randomly changes targets of spells. Warp World reshuffles the battlefield into something entirely different, which sounds really fun until doing it several times per game becomes someone's entire personality and you can't just not play with them because they're your friend and you hold out hope that they might get better one day. WE CAN GET YOU HELP, TOM.