If you're also a fan of Grimm, you've probably thought of doing this.  I did it.  Tell me what you think

Wesen
Wesen are semi-shapeshifters.  They can hide their inhuman natures when they want to.  As long as they’re not using their powers.  The more they draw on their powers, the more difficult it is to hide their true form.  I’m using Feeding Dependency as a model for the power, but it also includes other powers. They have 3 states.  Human form, Woge, and Display Woge.  Woge is involuntary and only visible to those with special powers, or extremely high Lore.  Display Woge can be seen by everyone.  And to anyone who’s not aware of the supernatural, it is a terrifying and scarring experience.

Woge:  Semi-shape change to the beast you carry inside.  Generally, only other Wesen can see you Woge unless you intentionally display your nature to everyone.

Hiding your form:  First, the sight sees your true self, so anyone using the sight will see a shadow of the Wesen form, aside from whatever else they see when you are in human form.  If Woged, the sight sees all.
Second, other Wesen can see you Woge. 
Third, high lore gives people enough info to notice a Woge.  A great lore check will notice the change without actually seeing it.  Higher scores will give more detail.  Epic (+7) sees it as clearly as if it were a Display. 
Beyond those exceptions, when in human form, or Woged, you are undetectable.
Mechanics:  when drawing on any power, you must make a discipline check vs the refresh cost of any power being used to avoid a woge.  This is cumulative in a scene.  Each time you use a power, you make a discipline check vs the total refresh of all of the powers used in a scene. 
Any time you take any damage, you must make a discipline check vs the number of boxes.  This applies to physical, social or mental damage.
All of the modifiers to the discipline check are cumulative.  So if you take 3 boxes of damage, and use supernatural strength, your discipline check is vs 7.

Display Woge:  Woging specifically to show everyone what you are.  This is usually done to stun people into inactivity. Knowing what’s happening greatly reduces its effects, but for the unprepared, it can have lasting effects, and even incapacitate viewers.
    Mechanics:  Woging is treated as a weapon 7 mental attack with a targeting of 1.  Defense is either Lore, or discipline -2.  So a fair lore check or a great discipline check avoids all damage.

Powers:  Vary by species, but some are common
-1 Woge
-1 Woging clears your physical stress track and reduces all physical consequences by one   level.  Reverting back to human form doesn’t do this. 
-1 Echoes of the beast. 
+1 Human form

Vampires:  Vampires find Wesen blood to be amazingly tasty.  There is no sipping of Wesen blood for most vampires.  They have to make a Good discipline check to not drain a Wesen to death. 

Origin:  Most Wesen originally come from Western Europe.  Not all though.  Many come from other lands.  But the society and social structure that most Wesen are a part of are from 15th century Austria. The names, traditions and rituals are mostly German, and regardless of where a particular kind of Wesen comes from, most individuals speak at least a little German.

In the US, there are 2 large groupings of Wesen.  Austin Texas and Portland Oregon.  Both cities are generally ignored by the major league supernatural players and are perfect for Wesen to live fairly normal lives.

Examples:  These are minimums.  Many have advanced beyond the basics.

Blutbad (wolf) - 9
Wesen -2
Inhuman Strength -2
Inhuman Toughness -2
-the catch is silver +1
Inhuman Speed -2
Claws -1
Pack instincts -1

Fuchsbau (fox) -5
Wesen -2
Inhuman Speed -2
Claws -1

Mauzhertz (mouse) -4
Wesen -2
Inhuman Speed -2

Hundjager (hound) -6
Wesen -2
Inhuman Speed -2
Claws -1
Pack instincts -1

Eisbiber (beaver) -3
Wesen -2
Pack instincts -1

Hasslich (troll) -6
Wesen -2
Inhuman Toughness -2
Inhuman Recovery -2
-the catch is fire +2
Inhuman Strength -2

Fuilcre (Ox) -6
Wesen -2
Inhuman Strength -2
Inhuman Toughness -2
-the catch is Yew +1
Claws (horns) -1

Siegbarste (ogre) -10
Wesen -2
Supernatural Toughness -4
Inhuman Recovery -2
-the catch to both is fire +2
Supernatural Strength -4

Ziegenmenschen (goat) -10
Wesen -2
Supernatural toughness -4
Inhuman recovery -2
-the catch to both is hemp +2
Inhuman Strength -2
Claws (horns) -1
Pack instincts -1

Hexenbeast (witch) -12
Wesen -2
Inhuman Strength -2
Inhuman toughness -2
-the catch is   +1
Inhuman Mental Toughness -2
-the catch is individual -0
Thaumaturgy -3
Channelling (spirit) -2

Wendigo (Canibal spirit) -11
Wesen -2
Feeding dependency, connected to
Cloak of shadows -1
Inhuman Strength -2
Inhuman Speed -2
Inhuman Toughness -2
Inhuman recovery -2
 -the catch is bone/teeth/claws +2
Claws (claws and teeth) -1
Demonic co-pilot -1
Flesh eater (same as blood drinker)
This appears to be a possessing spirit.  They may have been Wesen before they were possessed, and now only woge as Wendigo.  Or, it’s just like the old stories, and a man who eats human flesh becomes possessed by the wendigo spirit.  Either way, there’s a murderous spirit that demands human flesh inside them.. 
The spirit is always close to the surface.  Wogeing always engages the spirit.  Eating flesh calms the beast. 

Tags don't cost Fate Points; that's what separates them from normal invocations. I'm guessing this is meant to be a standard invocation.

I meant to Invoke not tag.  Thanks.

Generally not worth it to use an Aspect just to avoid stress, for what it's worth.

Yea, I was just going showing the kind of thing you could do with aspects.

Neither maneuvering nor shielding is a supplemental action. Both take your turn.

OK.  It felt wrong when I read over it.

Castillo still gets to take an action, even if his skills aren't good enough to make it worth much.

I said that poorly.  He did try, I just didn't want to spell out the mechanics on that one as I felt his Rapport of 2 didn't have much of a chance to overcome a Wizard's conviction.  The Wizards was there for one reason, and it wasn't to discuss motivations.

Also, you generally have to roll to put up a shield. Spellcasting is actually a multi-step process, involving gathering power and then controlling it.

I skipped detailing that part.  But yes, he rolled, and put up a force 4 shield with 2 exchanges of duration.

On a tied maneuver roll, the resulting Aspect is fragile.

OK, I didn't think about that.  Still get the one free tag though, which is all I used.

Given that Castillo has Athletics 5 and some level of Speed, he'd be better off defending with Athletics. Also, being a vampire, Castillo should have some amount of armour.

I actually did think of that.  He was trying not to use any of his powers, to keep his hunger low.  And he figured he could beat a Wizard in a sword fight without drawing on the blood. 

So the shield provides armour 4, with sufficient duration to last through the round where Castillo didn't act? Quite a powerful spell.

Sorry, it was a 4 point shield with two rounds of duration.  Not 4 points of armor.  That would be powerful.

Did you mean Inhuman Strength when you wrote supernatural?

No, he's upgraded.  That's why he got +4 to his damage.
This is an NPC I'd already made for the groups first adventure.

Armour usually doesn't stack. Actually can't remember whether armour from an Evocation is an exception; it hasn't come up in my game for quite some time.

But a 4 point shield would still soak 4 points before being blown up, and then the 2 points of armor would soak more, right?

Again, Castillo should have armour and a better dodge roll. And with Toughness, I'd expect him to have more than four stress boxes.

I neglected the toughness when I wrote that.  Just a mistake.

Also, I don't see any reason to take a moderate consequence rather than a mild here.

Right.  If he'd already decided he was going to flee, it would be better mechanically to take a mild and 3 dots.  Again, he's trying not to grow his hunger track, for reasons, so if he can avoid using his toughness or healing, he will.  Also, of course, two wizards facing down a 600 year old vampire would use magic.  I mostly just wanted to get in to aspects, and things you can do other than throw a punch. 
Thanks for all the help.

They spell it out on pg 275.  It says you need the whole Wizards package BEFORE you can start branching out with powers.

It's a submerged power level, so I can spend the 9th refresh for Vampirism.  Taste of death, in combination with supernatural recovery would be amazingly powerful.

edit -> But vampirism doesn't fit my picture of the guy.  He's not one of the damned.  He doesn't see people as food.  He's a protector.  I don't really even like the feeding dependency, I'm just trying to find some way to model the "some times he just hulks out" behavior mechanically.  I guess I could just drop that whole thing though.  His Trouble is The Demon Inside.  So between that and the demonic co-pilot, we could model it pretty well I guess.

OK, I did some changing around again.  If anyone is still here, this is what I think I'm going to go with:

Powers/Stunts -8
Echos of the beast -1
Supernatural recovery -4
  -Catch +3 (silver)(everyone knows silver hurts werewolves)
+1 Feeding Dependency affecting the following Powers (does not include the bonus refresh):
+1 Human Form
   - Beast Change -1
   - Inhuman Strength -2
   - Inhuman Speed -2
   - Claws -1
+1 Human Form upgrade: Involuntary Change(When taken out by Hunger; in the presence of blood; or at times of stress(GM dependent) (affecting):
  - Hulking size -2
  - Demonic Co-pilot -1

The Demonic Co-pilot both gives a boost to everything, and fills him with a rage and a need to kill.  I think it will be fun.

Yea, I like where you're going.  Except:

The way I understand it, that 10 point stress hit would just force him to feed, right?  That's what I was thinking anyway. 
The idea is, when he hulks out, the blood lust is upon him, and he wants to bathe in blood.  Pretty much like the Loup Garou. Mechanically, he's just going to have to make a blood frenzy check every single round, until he fails or the GM just compels it.

The rest of the time, under stress, he's actively trying to NOT hulk out and kill everything in sight.  If he fails a check and goes Blood Frenzy, he automatically shifts into the Garou, or Windigo form and chews on someone.  Or everyone. 

He can even do it on purpose, I think.  But again, when he shifts, it's like dropping a grenade, and friend and foe alike are endangered.

So, he always has Inhuman Recovery and Echos Of The Beast.
In wolf form he adds inhuman speed, inhuman strength and claws.
In Windigo form, he adds hulking size and supernatural toughness.