A big part of what defines such mantles is the authority and influence they grant the bearers.
This is more true for some than others, of course. For example, the mantle of the Merlin of the White Council grants immense power to the one who wears it. It doesn't, however, as far as we know, grant any magical boost.   

It seems to me a lot of the disagreements/arguments in this thread are being triggered by a missunderstanding of descriptions/definitions.

Definition 1 (Not unique to the DV): A figurative cloak symbolizing preeminence or authority <accepted the mantle of leadership>

Definition 2 (Unique to the DV): A power/ability obtained (willingly or unwillingly through various means) by an indvidual. Said power/ability may influence the bearer. It may remove options to choice and/or influence the bearer's choice.

Some Mantles being discussed clearly fall into one definition above. Some fall into both. I believe the problem is arising from tring to compare Definition 1 and 2. Let me try to clarify...

So the Merlin example clearly falls into line with the first defintion. As does being the president of a company, or treasurer of a fraternity, or chief of police.

Becoming the Winter Knight falls into line with the second definition. Being the Winter Knight obviously influences Harry.

Becoming the Warden falls into both definitions. Harry has gained responsibility as the Warden, but he also gained access to intellectus of the island.

So I'm saying is; when trying to discuss Mantles, it is ok to compare the responsibilites of being Warden with the responsibilites of being President of the USA. It is also ok to compare the power boost gained from being Winter Knight with the Intellectus gained from the island.

Here is where the Merlin example falls apart. The Merlin of the White Council does have responsibilites and can direct the White Council, but as far as we can tell, there isn't any actual metaphysical power boost. Arther Langtry has just as much magical power as an individual with or without the position of Merlin.

Another way to look at it is this... Think about the types of powers that could be transferred on Halloween. I think we can all realize that just raw magical potential could be transferred (whole or in part) between individuals. If that raw magical potential was tied up with being Santa Claus, then if you get enough of the bits you are essentialy Santa Claus. You are what you eat. The same could not be said of being VP of accounting for Intel. VP of accounting isn't the type of power that can be transfered on Halloween, therefore it falls under Definition 1 and not Definition 2.

Speaking of which...Harry should track down whoever created Three Eye.

If someone could come up with a non-crazy version it could fundamentally alter the fashion in which humans interact with and defend against the supernatural community.

Granted - most vanilla humans would lack the mental strength to handle such a thing but I bet that someone like Murphy (or someone not entirely vanilla like Thomas or the Alphas) would be able to put it to good use.  Someone with great mental discipline from another 'art' and who was already comfortable with the supernatural world.

I always assumed that Victor got the black magic power up from outside, but created Three-Eye on his own or at least through is own machinations.

           The Outsiders can be drawn in the same way as the fetches. In BR, during the ritual entropy curse, Madge summoned HWWBh stating, “Let our need become the traveller’s road.” Her use of the black magic ritual became a destination point for the Outsider to travel to the mortal world.

Mortal magic can summon an outsider, but this isn't what the ritual Madge used did. She didn't summon the walker. The ritual used HWWBh to power the curse because Madge didn't really have any magic of her own to power the curse. HWWBh was the battery/power plant.

EDIT: Though this is a fine point and open for discussion. We've gone back and forth on it before.

I am still not convinced, despite Bob's comment to the contrary, that the mantle remakes a person.

[...]

Any change that occurred in Titania, and by extension, Harry and Molly, would be as a result of choices they made.

How about this. The Mantle really really really wants to change you. It is good at changing you. Every time you choose to use the power of the Mantle, it changes you a little. So the bottom line is that you technically have to choose to let the Mantle change you, but it is a very hard choice to avoid.

We the reader realize that Harry only manges to just get by, after getting his ass handed to him, but to the characters in Harry's world... holy hell, the dude must look seriously dangerous loose canon.

Harry came to this exact conclusing in TC when the old school tough wardens were hesitant to step up to a fight with him. Vader is cool when he is on your side

The Secret to the Perfect Tan by Kelly Hamilton

Around the World in 80 Seconds by Margret Dresden

Is there a set time when the DF Spoilers board will be updated to remove all the Ghost Story specific items and replace them with comparable Cold Days specific items?