Is It Permissible to Create a Fictional Mythology for My Writing?

Assalamu alaikum! I've been wondering-would it be haram to invent a fictional mythology for a fantasy world, as long as I don't actually believe in it, don't promote worship, and make it super clear it's just made-up? I've loved writing since I was little, mostly fantasy stuff, but lately I've been thinking about what's allowed and what's not. I've steered clear of including actual gods or divine beings. I asked a few AIs, and they all gave me different answers, so now I'm just confused. Any guidance, insha'Allah? Jazakum Allahu khairan.