For starters, if you haven't done it yet, I would recommend you to have a look at the chapter Voidcalling in the Fate System Toolkit (free download from Evil Hat: https://www.evilhat.com/home/fate-core-downloads/) This could give you a good idea of how magic with an inherent tendency to backfire or go awry could look like. Second, whatever the desired effect is, I would handle it through compels (compels solve everything, remember? :-) Any effect created with the sponsored evothaum would have an appropriate aspect (e.g. Crossroads Demon's Workings or similar) and the GM could compel you or even tag it for free at an (in)appropriate moment. Self-compels would be also welcome. That's my two pence, anyway :-)

Migrating the forums elsewhere (so that the content won't get lost) would be a very good thing. Or at least archiving it and making it available. As for Obsidian Portal, it's quite a comfortable tool for hosting games, even pbm-ones. Otherwise I don't care much whether the discussion will continue on a huge site like rpgnet or on something smaller. The group will always stick together, I suppose.

I quite like the idea of Voidcalling from Fate System Toolkit (official Evil Hat download page here: http://www.evilhat.com/home/fate-core-downloads/ ). Maybe you could connect the wolf to that idea. And make it how the Outside works in your game. Wronged by the Fae? It's easy to go over the brink and actually summon a monstrosity they would fear…

Generally speaking, Fate is better with cinematic action that mysteries. This article is dealing with that issue. Otherwise, I can't imagine myself GM-ing eight people but this can be only me.

Ah, the lecherous old man is playing his part well, I see. Thanks, Griffyn :-)

Well, not YOU specifically. Unless you want to, of course :-) I meant it generally, more like "someone" or "anyone". My grasp of English may be weird at times as it's not my mother tongue.

A compel worth its name (and a FP) should always somehow complicate the life of the character or limit their choices. Having the player roll, succeed and get a FP is very weak in my opinion. Maybe you should discuss the exact nature of the compels with the player but when a compel is there it must hit the character in some way. Should the player insist on rolling, both results should still represent a clear disadvantage or limitation. This doesn't always have to be sucking someone dry or baring the fangs in public or whatever but the compel must be really felt as a complication. If the player doesn't want the character to be compelled this time he should pay a FP. Otherwise, wham! The only problem I can see here is that, generally, Fate is good with cinematic action rather than mystery. This can make some approaches easier than others. But then again, it's up to you as the GM and the player group to decide how often you want the compels to be happening and their exact nature. Btw., a nice compel concept has just come to my mind - what if the PC can sense a "calling" of the Red King and, if compelled sucessfully, tends to act in accordance with this subtle inner voice, furthering the Red Court agenda? A fine "invisible" complication, isn't it? :-) But you should have the player's placet for this.

Two options, basically:
1) Solve it as a block. I'd subtract the rating of the threshold/ward from any (reasonably affected) magical effect and call it a day.
2) Solve it as a compel. I'd just compel a relevant aspect (e.g. the High Concept of the caster) and let the effect be somehow affected by the threshold/ward or fail utterly. This option allows for more narrative freedom. Worth a FP, of course. If the wielder is the one affected by the compel rather than the caster the FP should go the wielder's way.