a) He's a dragon, so he breathes fire, has claws and flies. We also can guess the general shape of his true form.
b) His physical form is so vast and overwhelmingly powerful that it would shatter mortal buildings and minds alike.
c) He's a shape-shifter that can at least take human form, most probably other forms too.
d) He has powerful thematically appropriate magical powers. And by powerful, I mean that a casual word can take out the average wizard.
e) He is several thousand years old, comparable at least to some of the old pagan gods.
f) He's powerful enough that Mab would not want to take him on, at least not in a fair fight. So he matches the entire White Council, perhaps more.
Never a fan of Pen and Paper RPG's, so this is a fluffological response.
A-C. Does he have a "True Form" at all?
D. He laid Dresden out with his will, but so did Odin, the Red King and the Lords of Outer Night, when Dresden was much more capable.
. He's powerful, but within reason.
F. That might be a bit of a push. Mab would *accidentaly* turn the earth into a ball of ice if Titania wasnt matching her strength. Titanias enforcer can blow a denarian to pieces with little more effort than flicking a finger, and has beaten three senior council members.
Ferrovax might be strong, but he aint a planet killer.
Hell, a Knight of the Cross has offed a Dragon.
True, not all Dragons are slain equal.
Jim has said on this site that Ferro is one of the few beings able of going toe to toe with Mab, and supposedly said at a book-signing that Ferro is superior to Mab in strength.
I think he may have talked himself into a corner with that one then.
We've been told that the two Fae Courts fighting themselves into a stalemate keeps the world going round, if Winter or Summer overthrew the other, the effect on the world would be apocalyptic.
The only way Dragons fit into that as equals is if they're something like the great old ones, not of Earth.
Or of course, if the Fae number rather more than we have been led to believe to far, the queens might not be that far above Elder Gruff and co.
Harry at Storm Front was submerged. He could barely take on one lousy demon.
Harry at Death Masks is considerably stronger. One of the weaker Denarians is in his league or just a bit over.
Harry at Dead Beat has grown in power. He almost matches wills with Corpsetaker and captures the Erlking.
Harry in Small Favor kicks serious ass. Magog, Thorned Namshiel, Tessa can attest to that.
(changes spoiler) Harry in Changes as Winter Night is major badass. It takes an entire group of the Lords of Outer Night to contain him.
So yeah, I doubt he's still anywhere near submerged level.