I have a fae character in my back pocket who has a fairy quote from A Midsummer Night's Dream for all five of his phase aspects:

"Shrewd And Knavish Sprite", meaning general trickster-fae shenanigans
"What Fools These Mortals Be!", meaning the obvious
"If We Shadows Have Offended...", meaning that he's really not a bad guy deep down, he just kind of goes overboard sometimes.
"Give Me Your Hands, If We Be Friends", meaning that while mortals, as a rule, suck, there are some individual ones that are pretty neat
"I Do Wander Everywhere!", meaning he's been all over, seen everything, but has no real home

Bear in mind, it's totally possible to have "Unknown [+0]" as a Catch.  I mean, take, say, an elephant.  That's at least Inhuman Toughness.  But there isn't anything that would render an elephant as easy to kill as a regular human that would not work on an animal of similar toughness.  Yes, you can kill an elephant with a lot of weapons, but elephant guns also do just as much damage to bears, or to people.

And yes, the book does say every Toughness power has to be attached to a Catch, but frankly, if it's +0, it could just as easily be "A 24K diamond that's been in the center of the sun and only I know about this weakness", in which case making it "Unknown" simplifies everything for all concerned.

Acronym check: RAW?

Rules-As-Written.

Here's how I did it for my fae trickster that's sitting in my bag of character ideas:

Play as a fae servant bound to the party's wizard (sort of like Bob, only not stuck in a skull).  Say the wizard's great-grandfather did a big favor for Titania a while back, and she granted a vassal for him and his descendants.  Work out the specifics with the other player; give them a decent working relationship, the fae gets days off, allowances for danger, etc.

As for the whole "free will" thing, if it looks like a duck, smells like a duck, and quacks like a duck.  Give him a contract clause allowing him to ignore the wizard's commands in certain cases, give him stuff he likes to do on his days off, give him some basic personality traits, and it'll be close enough.

Since this setup relies on there being a wizard in the party, fae magic would probably be redundant.  Instead, I suggest maxing out Deceit (since Greater Glamours can be done with Deceit or Discipline), and assuming the role of "face" and/or illusion support.  Add a stunt that boosts Deceit when you're not lying directly to represent the fae's whole lying-while-telling-the-truth thing.

In essence, this setup could leave you rolling +7 Deceit in a lot of social situations, plus rolling +7 on veils and glamours, while still leaving plenty of refresh and skill points for balancing your role.

"no-lying" thing: treat those as compels on your High Concept.  This could also apply to things like thresholds.

Cold Iron: With a cold iron Catch, Supernatural Recovery would only cost -1 Refresh, and it's a really useful power.

Give Sam Feeding Dependency (demon blood) governing Channeling (spirit).  It'll represent the telekinesis he gets when on the stuff, and mental spirit attacks can represent the psychic demon-killing.

Now, if we could only stat up Castiel...