Alternatively, we could give Evil Bob the mantle, then have Matthews seal him away until we can bind him into a fetish. Probably a scythe or a gun, though a book might be a cool possibility if we were intending to use him more for the knowledge rather than the Ankou powers. Be a great Christmas present for someone. Or bribe for Mab if she's mad about us stealing the Mantle.
This is a catastrophically bad idea.
Evil Bob's personality had no trouble aiding Cowl when he was prepping the Darkhallow to kill a couple million people.
Investing that with divine power and authority is like giving an ISIS chieftain a working nuke.
If Arawn gets away without being killed he should still hold the inactive Mantle, and we're probably only months away from having our own personal afterlife and wardens of dead souls. We don't need to jeep him out of Mab's clutches for long.
There is nothing in the wording of our charms that suggests we need a god of death to babysit our Hell.
You're suggesting drawing the antagonism of a magical player a lot bigger than we are for something we dont need and cant use.
Because reasons.
Honestly I wasn't expecting to get to keep it. much as I might want to. I was mostly thinking "who will we not feel bad about handing over to Winter?"
From a certain point of view a weapon that comes with a built in encyclopedia and can be handed off to anyone on a mission likely to come into contact with necromancers is better than a historically flaky guy. Depending on how well it's made Mab may very well count herself as getting the better of the exchange.
You have a point about the risks of powering up EB, but if he's bound beforehand using methods that can handle the state change it should be managable.
A god is not a weapon, its a player.
I think you would be unpleasantly suprised if you expect to invest a spirit of knowledge with a mantle of Death and expect it to remain something you can command.
Mab almost certainly doesn't know quite what an Exaltation is or what it can do. If she did she wouldn't have left one imprisoned next to Slade.
As a result, she won't know how powerful Molly is or what her capabilties are. All she'll know is that Molly is demonstrating multiple significant abilities. She probably does know what a Yama King is, and that they're powerful. The Exaltation stinks of Yomi Wan, and Molly will relatively soon unveil that she's the Yama Queen of a previously unknown but also presumably existing Thousand and Oneth Hell. You don't need a mantle to exert power in the Nevernever, which means that it could be very dangerous for Mab to go after Molly there, as what makes Mab strong is that unlike most of her peers she has a Mantle that still allows for significant influence over the material world.
What makes Moly even more dangerous, as unlike those other great powers of the Nevernever who, as I say; are strongly limited by their mantles in how much they can interact with the material world. Molly seems to have found a workaround and is able to exert significant power personally, in a realm where even Mab is seriously handicapped.
Note that the reason Hades no longer has much power relating to the material world is that people don't believe in ancient Greek religion anymore, which also means his afterlife is relatively empty. Billions of people do believe in the Hells of Hindu, Buddhist, and Chinese folk religious mythology. That should mean that the Yama Kings should be more powerful than ever and their Hells will be swollen with souls.
The changing of the guard due to the rise of the Abrahamic religions that has lead to the European, American, and probably African mythological pantheons being sidelined hasn't happened in Asia, which should be a serious worry to Mab.
Molly isn't actually that strong yet, but Mab is unlikely to know that, so Molly can probably bluff until she is. Particularly if she does things like demonstrate she rules an Afterlife.
And a mantle like that of the Eldest Ankou would be a really useful thing for Molly to give to one of her devils when she had them, as they're probably bound by the local metaphysical restrictions against entities of the Nevernever messing with the material, and having one of her devils being able to hunt necromancers would be very handy.
1)Mab has dealings with everyone from the Archangel Uriel to the surviving Great Dragons to the Archive.
If she needs to, she can find out. And probably faster than we can, actually.
Assuming she doesnt already know; the thing was buried in the heart of her power for xenturies, so she got a very close look at it for a very long time. Hell, for all we know, Uriel sent Mab a briefing dossier; the woman commands Earth's defenses, so she might well have need to know.
2)My brother in Christ, Mab is powerful enough to wipe out the whole White Council, including the Senior Council, at once.
Powerful enough to party wipe the Red Court, by herself. By Word of Jim. She's not powerful because she's the only person able to act outside the NeverNever, she's powerful because she is Mab.
Those in her weight class are people like her sister and Ferrovax. Possiboy Ethniu, but Ethniu is a special case.
The only people more powerful than her are in the category of the Mothers and Angels.
3) Human remembrance grants continuing access to the mortal realms, not power. Very few people know of Ferrovax personally, which doesnt make him any less a Mab-tier Power or prevent him coming to Earth. Power in the mortal realm has nothing to do with mortal belief, else the Hindu pantheon would be major players, and they dont appear to be.
The White God just made the rules, and everyone else has to live by them.
4)We dont know how the Yama Kings work in this AU.
Just that Mab's forces thrashed Enma-O's armies and took the Exaltation from them when they met in the field. Which should tell you all you need to know about the relative tiers of power in this alternate Dresdenverse setting, when the side using a McGuyvered Infernal Exaltation as a weapon lose.
5)Bluff is not a thing you want to do to the Queen of Air and Darkness.
6)Zero indication that Molly has any need for any of that.
And if for some reason necromancers are a particular bugbear of ours, the White Council has never needed a god of death to hunt necromancers. They send war-parties of Wardens with no radios to do the job.
You're basically trying to reverse-engineer a justification for grand larceny.