Perhaps it's not (yet) permanent - some level of maintenance is required to keep it from returning.  Or perhaps it's simply addictive (in which case someone else may have trapped the vampiric rage in the item).

How would the item work?  While making it similar to an IoP is probably easiest, I'd modify it if you want something addictive or requiring maintenance.  Addictive is easiest, there are models in the book already.  Maintenance could be done through aspects fairly easily or a reverse hunger track of some sort.

Why doesn't he just toss the item away?  He's an addict, afraid it will return to him, or possibly knows it will infect someone else if he can't find a way to destroy it.  Or perhaps he's tried to throw it away and it simply reappears in his possessions...pulled by some link he hasn't managed to sever yet.

Does he still need to feed?  Addiction or maintenance could take the place of feeding. 

How can the Demon try to escape?  Influence others...what else would a WCV's demon do? 

If he DOES cure himself, where does the character progress...does he become a mortal? (that seems...less fun)  That's cannon but it's your character.  What do you want to occur?  Perhaps the beginning of a new supernatural race?  Or at least aberration.

How do you frame a combat scene?

In general, I don't need to; it grows naturally out of the preceding scenes and choices. 

When you are initiating the scene without benefit of previous scenes' context, I recommend starting as late as possible.  Don't begin with a monologue describing the last hour they've spent investigating the club's White Court connections, begin with the moment the dancers become suddenly aggressive and the PCs are caught in the spotlights.  Right as the fight starts in other words.

My question was how should I create a combat scene. Like A-team vs B-team, simple. The thing is that for some reason I cant come up with a convincing combat sequence. The aspects for example, how do I choose them?. Give me an example of a combat scene.

Don't get hung up on creating poetic sounding aspects, just consider anything which may affect the outcome an aspect.  Is it dark?  Crowded?  Overwhelmed by loud music?  Or is it a well lit city street lined with parked cars?  Your scene aspects are the pieces you (or your players) think are important pieces of the description.

One comment on the earlier discussion about the "difficulty" levels of thaumaturgy.  Counting shifts has little to do with difficulty.  Shifts beyond a relatively low number are accounted for by declarations - basically convincing the group that a given aspect sounds good and rolling a die (or paying a fate point but the die roll costs nothing).  Any difficulty is purely in the group convincing part.     Shift's are not even a good representation of time consumed since declarations are often about something done in the past. 

Regarding thaumaturgy being used to create a justification for powers, I'm ok with a permanent spell.  However, an invoke (or tag) is still needed for each scene it's used in unless you spent refresh on it.  Two reasons for that: one those are the rules (see the sidebar referenced earlier in the thread); and two is keeping the archetypes relatively balanced.  Or at least no more unbalanced than they are in the text. 

There are, of course, as many different ways to approach the issue as there are groups. 

Okay, I've got your point. I can't say I agree, but let's presume I share it. What would you treat as a sufficient condition to begin recovering from something like "pyrophobia" as a moderate mental consequence?

What level of consequence?  Mild fears may go away with just some time to think out issues and ramifications while moderate fears may require physical evidence (such as Taran's trip to the fire station) or even counseling.  Severe fears probably require treatment or even drugs...and may never go away completely.  What makes sense to the group in context?

-When to use an Invoke for effect vs when to Just tag for the +2

This is easy if you invert the question - use an invoke when you want to add to a die roll; use an invoke for effect (aka compel*) any other time.

-Examples of invoking for effect that you've used or come across.

Any change, narrative manipulation, or (quasi) forced temptation / complication to environment, characters (PC or NPC), scene, or game is potentially a compel / invoke for effect.  Specifics are negotiable.  Negotiating instead of simply saying yes/no is forgotten too often.   

Examples include compelling a character with "Boisterous" in an aspect to be loud at inappropriate times; compelling a character with "Curious" in an aspect to be nosier than etiquette demands; using a "Dark Room" aspect to ensure actions are concealed (at least from those affected); and using a "Bureaucratic Nightmare" aspect to ensure legal paperwork is misfiled.  Examples are only limited by imagination and by what makes sense in context to fellow players.

-Any Limits for Invoking for Effect

Group consensus is the real limit, they should make sense in context. 

-Any advice or wisdom, in general, that you may have.

Use them!   

*Fate Core drops the bombastic jargon of 'invoke for effect' and the complication of having two terms for the same action dependent on who initiates it.  Compels are 'invokes for effect' and 'invokes for effect' are compels.

Has anyone else used laboratories in their games to restrict/complement Thaumaturgy?

Yes but just as an aspect ("Well Stocked Lab" or equivalent) to use for the spell.  A Resource declaration in other words.

Here's a slightly different take on the Jade Court:  Also called gaki, preta, jikininki, or simply hungry ghosts, Jade Court vampires prey on humans to remain physical. In their natural state, gaki are ghosts, spirits of hunger. To live, they dominate and possess humans, slowly eating the dominated souls. As time passes, the possessed bodies become thinner, only-bone-and-skin, emaciated human beings with bulging stomachs and inhumanly small mouths and throats.

I wrote that one intending to scare White Council wizards.    Hard enough to kill a regenerating spirit, even harder when it thinks you're a tasty snack and habitually possesses otherwise innocent humans.

In the long run you'll want to create or choose a version which fits your concept.  There are far more answers than one or two.