So my favourite theory is that Cowl is future Harry, but recently I have been entertaining another idea:

Cowl is time traveller Billy and Kumori is his daughter.

So what leads to Billy becoming a dark overlord?

During one of the next Books (Peace Talks or the one after Mirror Mirror) Georgia dies. Billy is devastated and starts researching for ways to bring back the dead. In the last case file Harry defeats Cowl and recognises Billy. He hurries to Billy to stop him from becoming Cowl, but, when Harry frantically knock on his door, Billy panics and time walks away with his daughter.


So indications to this theory:

• During Dead Beat when the Alphas approach Cowl runs away. This isn't because he is afraid of them, but he is afraid of a time paradox or at least Georgia recognising his smell
• Additional during this scene Cowl chuckles about Harry calling him Darth Bathrobe. Billy is probably a fan of Harry's Humor.
• After the Darkhollow blasting of in his face he was probably badly hurt. Billy is shown to have started developing self healing. He is the only character we have seen doing this on screen till now. (Although LTW probably can do this too.)
• When first see the Alphas Billy proposes a plan to go ahead and kill the FBI Agents. He is introduced as liking the blacker solutions, but Georgia is his backbone and moral compass
• Kumori probably never really gets to know Harry.
  So in Dead Beat she is curious about the guy her Dad told her so much about.
• From narrative point of view this allows us to view Cowl's slow descent
• Also from the narrative point of view, it us smart to introduce the main antagonist in the second book. The loup garou might get relevant again but I doubt he is a villain. That only leaves the Alphas.

So feel free to tear into this theory.

So if Cowl ends up being a time traveler could the gift be part of Ferovax Hoard from the future?  This would send an interesting message to Ferovax as he would know it can't come from a point in the past or the present.

It's saying, hey, we either killed you and got rid of the curse or you gave it to us willingly. So don't mess with us. We are either to strong or your friends.

Well I have to agree with this theory. I have some ideas on possible fixes for problems with this theory.

First an idea that contradicts some of the points: Harry was the attacker on Arctis Tor with Lasciel's coin, which he fetched from the circle.  While doing this he realised that LC isn't fixed and that he has to be the one who did it. Sadly I don't have a good reason why Harry attacked.

For the alternative with Harry being part of the defence I came up with the following reasons: Something, which feeds on blood, is sealed under Arctis Tor, more precisely the court room. I think most of Mab's big scale rules are pure logical and so there has to be a reason why only blood shed is forbidden in her court room. When the blood of the ogre hits the ground in CD the whole ground begins to tremble, at that moment it seems logical as a mirror of Mab, but if a sealed something would be revealed, it still fits. If nemesis is really interested in freeing this being, the whole court room scene might be seen as a attack too. If Harry would have snapped and splattered the ground with the ogre, it would have been game over right there. One last hint at something under the court room is the trapdoor and Harry wondering what is down there.

About Thomas being the assistant I think it might be possible. I (and I think some others here too) have played with the idea of angels being wardens working across time lines. As hinted in Changes mouse belongs to this group too. So when Mouse and a time traveling Thomas (Alliteration so it has to be true) they are allowed to do so by the time wardens.

About abilities for the placard: It could show the true name of anybody carrying it.

About the Hellsword:
Maybe it is not a sword, but the Athame. It is a equal trade to Amoracchius and Harry questions if it is in league with it. And i mean a evil dagger would be much more fitting for backstabbing evil guys And since time is not really a matter to archangels before and after humans don't matter.

About the wardens swords:
When Demonreach waffles about the Warden he says that at first there was only one and then there were many. So what if Merlin locked away all the big bad guys and then realized that there are still plenty of bad guys out. So he picked up the shards he still had stored away safe and does some powerful magic on them that bends their purpose because now they are able to kill innocents. He then teaches the leader to be of the wardens how to make the swords and seals himself away.
Why is it such an hidden spell?
1) Making more swords would dimish the power because they all tap into one power source.
2) Bending the purpose of something this powerful could be bad
3) Knowing how to create something probably means you can undo it to.