Can’t use the trademarked terms and whatnot, but creating things in the style of seems legal.
It’s like reading Tolkien books for 1000 hours and then writing a book that’s inspired by Tolkien.
Or like making a painting in the style of Picasso, etc etc
"Derived work" does NOT mean "copyright of original does not apply".
It means "copyright of original DOES apply, in addition to copyright on the modifications."