I suppose I need to try to be a bit clearer. I'm not saying that the Fallen don't have real power, they do. But, primarily what they offer to any of their hosts -- even Magog -- is knowledge. Cheat codes for existence, for the small price of your soul.
The Fallen are consummate liars as well. The exaggerate and misrepresent what they actually do. The purpose of these lies seem to get their hooks into you more and more, until you submit to being an actual agent of Hell.
Let's say that the Fallen teach you to shape shift into a Grape Ape. Grape Apes are awesome and lots of fun -- you get to throw barrels at little Italian plumbers and stuff all day. But, the Fallen says -- if you toss my coin, you'll never be Kong again. You believe the Fallen, because you couldn't do that before the Fallen. Now you use or toss the Coin and because of your mistaken beliefs you can't go Kong anymore because you don't believe that you can. Dumbo's magic feather. You might know how to do it still -- in fact, I think you do -- but you don't believe that you can do it, and belief is all important to doing magic.
Harry actually talks about this concept all the time, but he rarely thinks about its wider application. His duel with Hannah Lasher is an exception. He contemplated that Hannah believed that she was more powerful because of Lasciel, but really it was because Lasciel riled up her rage. Hannah could have learned to do even more potent fire magic on her own. Harry exposes the "cheat code" approach for what it really is, because while Hannah's attack was more potent that Harry's defenses, Hannah didn't have the depth of experience and broader skill that comes with hard work. And so, Harry essentially tricks Hannah into killing herself.
Yes, but not everyone can become an Alpha, there is some other stuff going on as well. If you don't have that pre-existing talent, without a coin, I don't think it is going to happen. I think the bigger question is why do you think you need to turn into anything with the power and strength that comes with it? That is the temptation, Nic is very careful to match potential hosts with their coins, he had good reasons to match Lasciel with Harry.
Are we sure that not everyone can become an Alpha? Because the odds of a half-dozen or so friends at one particular college in Chicago learning to become werewolves at exactly the same time is pretty unlikely -- unless, literally anyone can do it if they have a teacher.
Further, while Nic is "picky" about his flunkies, Tessa is notably the opposite. She'll give a coin to whoever, seeing the people as disposable.
Yes, if he worked at it, but then again how many people teach conversational Etruscan these days? Yes, with Lasciel's help Harry could and was able to understand the Ghouls.
Yes, precisely. And, keep in mind Lash didn't actually TEACH Etruscan or Ghoul, she just translated UN style for him. Now that she's gone, so is his translator. She could have taught Harry Etruscan, but it probably would have taken a few weeks or months. If she had, Harry would still know how to speak Etruscan.
I think that if you review their time together, Lash constantly OFFERS to teach Harry things, if he only formally takes up the Coin. But, she actually teaches him very little.
She did teach him a pain suppression technique, which he has used since Lash departed. She rarely gives away knowledge, as its her only lever.
No, you pretty much lose whatever skill you got with the bargain. Look as Cassius, first things first, when he gave up his coin, he started to age rather rapidly to whatever his real age was.
Is that what really happened? Or is that just what Cassius believed happened? After having been told for two-thousand years that he would age and swiftly die if he lost his Coin, did he come to believe and then his belief made it real?
He didn't loose all of his Coin-acquired skills either as he could still do magic and produced a death curse at the end.
One more metaphor to suggest somewhat of a compromise or synthesis of our theories:
Let's say I've been cast in a new movie -- the 600 Hundred -- which will be like 300 but with twice as many people. I'm a big guy, but sadly a bit doughy around the middle now that I'm closing in on 50. I could get back into shape, but it might take three or four years. Besides, I don't myself have the knowledge about fitness and diet, etc. to turn myself into a Hollywood Spartan and just figuring all of that out could take me years all on its own. Thankfully, the studio has that knowledge -- personal trainers, chefs and ... ahem ... pharmacologists eager and willing to help. In six months time, they whip me into shape so that I don't look out of place next to Leonidas or Creepy Persian Man. Now, replace those professionals with Fallen Angels telling me exactly what to eat, how much and when and knowing exactly what exercises, weights, reps and times will give maximum results. Now, instead of being movie buff, I'm super human essentially and the star of the movie now.
After the movie is over, the trainers, chefs and drug dealers have all left (or alternatively the Fallen Angel). I can't keep up that level of fitness anymore. But, I've learned a ton and with some effort I can keep it up at least to a degree. Maybe I can't be as fit as I was with those true professionals guiding me each step of the way, but I'm a great deal more fit than I was before they came and left.