I'm trying to think of a chaos god who actually fits the stereotypical role in fantasy, and honestly, a lot of authors use 'chaos' as a cheap excuse for arbitrary plot twists. If the chaos deity just randomly screws with fate because it's 'funny' or 'chaotic,' the story loses tension. It feels like the writer throwing dice instead of building a meaningful system. A better approach, in my view, is when chaos embodies a principle of pure potentiality—the god doesn't overturn fate out of malice, but because fate itself is a rigid script, and chaos is the force that writes in the margins, offering unexpected exits and entrances. It makes mortal choices matter more, not less. The trick is showing how characters navigate that unpredictability. In Roger Zelazny's 'Lord of Light,' though not strictly a chaos god, the underlying cosmic forces operate on a kind of karmic randomness that characters must outwit rather than beseech. That feels more authentic.
Where I see it done poorly is in some pulpy series where the chaos deity is basically a deus ex machina with a cackle. It undermines the whole concept of destiny if any prophecy can be voided by a divine tantrum. But when done right, the chaos god's influence isn't about breaking fate but complexifying it—fate becomes a tapestry with threads pulled loose, and the real story is how mortals weave those loose ends back in, often creating a pattern the original prophecy never envisioned. I just finished a web serial where the 'God of Misrule' didn't change the outcome of a foretold battle, but introduced a third faction that forced the two prophesied sides into an uneasy alliance, which was way more interesting than a simple win/loss reversal. That's the kind of chaos I find compelling: not negation, but chaotic addition.