Odd question arises.
The local faerie court's members are similar in appearance. Can the Tytalus supernatural ability Persona be used to emulate the faerie's appearance?
Odd question arises.
You can use it to emulate their appearance, and it will be good enough to fool humans. However, any faerie with Faerie Sight (from RoP:Faerie) will be able to see through it automatically, as they can see through illusions no matter how strong or weak the magic is, and Persona counts as a magical disguise.
Just adding to darkwings's reply:
However, they (the local fae) might decide to play along.
The description of Persona does mention that you get a reputation in the community where you develop the Persona. So if you develop the Persona to apply in the Faerie Court, I keep wondering what might happen.
If nothing else, a Reputation in the story of a faerie court should promote your story element worth. Or some such (Faerie motivation keeps slipping from me). Or perhaps the Persona might get trapped in the Faerie court's story.
Of course, there is the problem of the cross-Realm interactions between magical Persona and Fae.
Addedum: perhaps I should have said the as well as similar appearance, the Sidhe nobles seem to have similar personalities as well.
Are they, in fact, aspects/fragments/copies/something of the same fae?
I am undecided whether the "story" they are playing has a large cast but very few defined parts, or the two central high-noble figures (Lord and Lady) pulls the rest of the court into "understudy" roles.
My thought is that persona should work very well with the faerie realm (even non-courtly faeries) because while the base effect is magical what it produces is a non-magical effect very similar to a glamour, in which you take on a new "story", but which also ties into human (your own) vitality. As such faeries should be able to tell the difference, but at the same time should get a wellspring of vitality from playing along.
Persona is a disguise effect, but it's more than that, and I wouldn't classify it as an illusion power largely because the power is not a constant effect. It's closer to a momentary Muto corpus (mentem) effect similar to the Heartbeast but different, a power that allows you to shapechange (among other things). Faerie sight does not extend to seeing through shapechange, as far as I understand.