Harry Dresden is no longer allowed to show the Eldest Gruff the Happy Tree Friends ever again.
1) Even if he laughed himself silly over it the last time.

You could also throw in the idea of batteries.

Cool. Thanks for the input!

Right now I've worked out that Simon Magus is the first in the bloodline. I've got a pretty detailed bit of background for him that I think fits pretty nicely into his legend.

The 7th and latest incarnation will be an average 17 year old living in modern times.

That leaves five in between them, spaced out about 300 some odd years. Since the modern incarnation is caucasian, I'd like to not use anybody else who is. I've got two other incarnations that I definitely plan to use:

Koschei the Deathless. In my version, he's a Ket shaman with a suit of armor that looks like its made of fused human bones. (One of Koschei's nicknames was "Old Bones" because legends characterize him with a gaunt or skeletal appearance.) In the legends, Koschei got a bad rap for terrorizing virgins and maidens. In my version, they're actually demons in human form. Another possibility is that a scourge of incorporeal demons possessed young women throughout the countryside, as a means to prey on human males, and the only way he could save these girls' souls was to kill them, thereby exorcising the demons within. Obviously this didn't win him any popularity contests, but he decided it was better to save their souls and mourn their deaths.

The other incarnation I had in mind was Fafnir, the dragon. This Norse legend probably has an oral tradition dating back for many centuries, but since it wasn't published till around 700 AD, I have a little leeway to "fudge" and make the actual occurance take place sometime a few centuries before that.

In breif, Fafnir was a revered dwarf who changed himself into a dragon, collected a massive horde of stolen, cursed gold and was slain by the hero Sigurd.

In my version, the "dragon" is actually Fafnir's demon familiar, and she's not a dragon per se, but something big and awful, and able to control fire, so what else would they call her but a dragon? I'm toying with the idea of making Fafnir a human being of different ethnicity than the Norse folk, who has somehow ended up far, far from home. (Orphaned son of an Arab explorer who predated Ahmad ibn Fadlān by a few hundred years?) His dark skin and shorter stature elicit some xenophobic prejudices. This, coupled with some elaboration on the part of story tellers all work to make him the dwarf of legend.

Sigurd won't slay Fafnir or his familiar, but rather they'll work together to face some common foe. However, Sigurd ends up being a braggart who takes all the credit, and adds the bit about slaying Fafnir to boost his own reputation.

Details are still sparse, as this is very early in the developmental stage, but that's the sort of thing I'm leaning towards.

Make her a Sirrush.

There is a novel by Judith and Garfield Reeves-Stevens where a good guy vampire holds off a bad guy vampire with a cross. The bad guy believed that the cross could hurt him.

If you are worried about him becoming to powerful, give him a crutch. Perhaps he has to have a favored toy, book, or something on his person when he casts a spell. Maybe he has a "place of power" where he casts his spells; this place may have some favorite posters on the wall, collectibles on the shelves, or even a favored book in a place of veneration. Give him bad eyes, allergies, give him OCD, or perhaps he has a hard time focusing.

With the allergy thing, have it where he has to use incense, and when he inhales it in, he starts sneezing and screws up the spell/ritual.

With theiroanthops (weres) why not go the yokai path. Instead of people turning into animals, have it be animals turning into people.

Cool.  Then yes at some point your skeptic will have to sit her down and (if he were me) ask her to explain her beliefs, and then start pointing out the contractions (much like harry to murphy on the bible in the beginning of wn).  Once he has shaken her loose from her adolescent infallibility, she will be much more likely to be receptive to guidance.  But I do agree with the others that it will probably take a screw-up on her part to make her willing sit down and really examine things like that.  Basically, life shows her that she went wrong, skeptic explains to her where she went wrong, and then they just have to figure out what the right way is.

It would also be neat when the creature shows up again, she can see if for what it really is, and she works is over.