Miscellaneous bits that need to be folded in somewhere appropriate...

Characters exist either entirely within a campaign or outside of one. Characters can be copied so that they live in both places, but then there are actually two distinct characters that are modified independently of each other.

When cast members enter the stage, a copy of the character is created and manipulated as a proxy, with the original cast member becoming locked. This approach ensures that the scene can be abandoned, returning everything to its original state. It also allows the GM to treat many NPCs as reusable, with all changes applied during a scene being discarded (e.g. wandering monsters, bandit patrols, or any other script that the GM wants to use again in some fashion). When a scene is resolved, accrued changes to proxies are saved back into the underlying actor when the actor is persistent and discarded otherwise.