Pathi

Sure, it's rare, but why is it rare? That's where the color comes in. After a few thousand years, the blood of dragons could be found anywhere, so it's not limiting in the sense that we don't let non-Pathians have it, but it still is the hook for the ability.

If you look at the blood gifts, they do tend to limit a jack-of-all-trades aspect. Generally, you have to pay a lot extra points to get more than one line, so it's not unprecedented. If I recall, the Cibola one is completely exclusive of all others, in fact.

But to me, having the blood of dragons is a great story hook that is sitting out there to develop at some time.

However, there's a bigger question that is going to come up. Is Arcanis really something that someone can "pick up" in the time frame of the game? This will matter if an existing PC wishes to learn it outside of chargen. I know I have generally talked ICly about the years of study, and how we generally only take the young. For playability, I can see allowing advancement in almost all of the gifts, but what about the base ability of ARC-CT? It would seem to make sense for it to be a chargen-only ability, but I can see why we might let this slide too.