Neither would Hell-Walker technique. Akuma are not spirits. Old Chinese is not a language of spirits. The description of the charm is:
Akuma are not spirits.
But a bunch of spirits were. Hell, Mikaboshi is of human origins, and is now a Yama King. Yen Lo's successor was explicitly a female buddhist monk turned spirit.
Look at the story of the origins of humanity in Kindred.
Who the August Personage of Jade is supposed to be, and how the Middle Kingdoms are organized.
Then come back and tell me that Old Chinese is not a language of spirits.
As far as I can tell, it would give us an ability to talk to Porter's Indian cousin, not an ability to understand all languages. And there's nothing about written word here either.
I honestly have no idea where you are pulling "it makes us speak all languages" from. That's not what it does.
What you are looking for is Source Code Compliance Protocol. Because that's the charm where you gain access to "language at the root of all languages" and can communicate with anyone and everyone.
1) In Exalted 2E, the language of gods, raksha and sorcery? Is Old Realm.
Which is called Old Realm because it was also the language of the first human empire in the First Age.
And, IIRC, was originally inherited from the Primordials.
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2) In the Dresden Files, spirits all speak human languages, both between themselves and with humans.
Wizards dont need to learn new languages in order to communicate with them.
Ergo, if you learn the languages of spirits, you are learning the languages of humans.
Toot-Toot speaks English and Russian on-screen, and speaks in English to other wyldfae; Lacuna and the other wyldfae all speak English. So do the cobbs. Ulsharavas and Chaunzaggoroth speak English. Bob and Evil Bob spoke English and I think German onscreen, in addition to other languages offscreen; pretty sure Bob speaks French as well.
Bonea speaks English.
Odin speaks English and Norse, probably more. Hades speaks English and presumably Greek.
The Erlking speaks English. Shagnasty speaks English and presumably any number of Native American languages; he helped teach the Native American tribes stuff like language after all.
Alfred Demonreach speaks English.
Lash spoke English, ancient Sumerian and ancient Etruscan that we see onscreen. We see the Winter Court in session in Cold Days at Harry's welcome back party; they speak English. We see the Erlking's court in Changes; they speak English.
Ethniu the Titan spoke English in Battle Grounds.
The angel in Fidelacchius that spoke to her spoke to her in English.
Thorned Namshiel spoke to her in English as well.
Even the Outsiders appear to speak human languages, when they arent doing direct mind-to-mind bullshit.
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Furthermore, there is also the other function of
Hell-Walker Technique: Crossing into different layers of the NeverNever.
Which is kinda crucial if you are chasing someone in the Dresden Files who isnt a baseline mortal or low-level/focused talent.
Wizards, Rampires, Blampires, Whampires, Winter and Summer Fae, even the wyldfae, can all dip into the NeverNever.
Literally the only supernatural race I'm aware of that cannot do this as a native ability in the Dresdenverse are ghouls, and its implied in the RPG that at least one high-rank ghoul learned to do it.
If we're going to Vegas after a ranking Outsider agent like Sandra, in an area thats apparently a weak spot in reality?
Im leaning towards that being rather important.
Well, actually, yes, I would say that between "kill them" and "crush their minds with magic to make them complacent" Molly would at least hesitate which is better.
1) Its not a mind-crush, which implies a destruction of their volition.
Its a geas, a binding. A compulsion to obey.
Their volition hasnt been destroyed, just constrained.
2)Its
temporary.
Even the most efficacious roll only binds the subject for a year and a day.
When the alternatives are having to permakill, say, a lesser akuma whose soul is held and compelled by a Yama King, or a spirit that's geased against its will, or a child possessed by a demon or a bane, as compared to instead binding their volition for long enough to use Sapphire Exorcism to break the link?
Molly will pick Crowned With Fury every time. I dont think there's any contest there.
Yes and no, you have the metaphorical heft, but the thing is Molly has no idea how to perform soul trade safely. That can be overcome by experimenting, which is rather gruesome and not really in character, or finding the information somewhere. This in turn ranges from raiding or trading for it with a Yama King or other kind of greater demon to having a very deep think on your inner nature... probably involving a walk into the Labyrinth.
We have the body of the Will of Kakuri.
Im not seeing any mechanical impediment to using that as the focus for a Crown question to figuring it out. Indeed, the body or resting place of any of the akuma that died at the steel works, lesser or otherwise, would be a legitimate Crown focus for that question.