Time being required for change is a nomological necessity not a logical necessity, nomological necessities aren't necessarily necessary facts but are regarded as facts but can be dismiss as facts after a new scientific discovery is made.
Forms in the theory of forms can be changed despite being unchangeable and atemporal, this can only be a complied by a deity in Plato's views God.
If we wanna get technical, time is not eternal since that implies eternalism holds, by extension implying determinism holds as well. However quantum mechanics makes it clear and demonstrates if anything the universe is more probabilistic than deterministic, even if was potential infinity which doesn't imply eternalism it has a beginning.
If time is caused and not uncaused then it had a beginning, which changed time from not existing to existing which implies again change can happen independent of temporality.
I'm confused on the plot point, there are fictional characters beyond and can still cause change and atemporal fiction characters who can be changed and cause change themselves so.