Theatrics is playing a role. The other persuasion skills project the character’s own person at a listener, however manipulatively; Theatrics explicitly presents somebody else. Even the untrained can make an awkward attempt at it. Doing it well demands invention and vocal command both.
The skill covers three related tasks:
Acting — taking on another personality, real or invented. It may involve mimicry and disguise, but need not.
Mimicry — altering the voice to sound like something else: another accent, another person, a bird’s call.
Disguise — altering the appearance. Difficulty scales sharply with specificity, from +20 for looking like a generic member of some class or trade to −40 for impersonating a particular named individual whom the audience knows by sight.
Layering. When a character uses one of the other persuasion skills from inside an assumed role, that other skill is the one tested, and Theatrics applies only its Secondary Modifier. Walking past a sceptical guard in a stolen tabard tests Theatrics alone; standing there lying to him tests Guile (Theatrics).
Opposition. Against an idle target, Theatrics is unopposed. An alert target resists a physical disguise with Awareness, at 0 to −20 for distance; if they can talk to the impostor, they oppose with Intrigue against Theatrics to test whether the role holds up, ties among successes broken in the target’s favour.
Artistry. Not every use is manipulation. A performance’s aesthetic worth is a plain Theatrics Success Value test, its Value Diamonds measuring the impact on the audience exactly as Dancing does.