Much as GWM and the errata do not include the means by which the Fair Folk can protect those they favor from the Wyld (despite it being a Core ability), there is no official Charm that I know of which can be used to invest power into a mortal.

The Scroll of Heroes does suggest such a method must exist, of course, since Investiture is mentioned as a means by which one can become Fae- (or otherwise-) blooded. Since it's a text with a certain aura, this may not be acceptable to all GMs (despite being the only text describing fae-blooded).

So you have two options:

1) Homebrew Investiture charm, which really should exist but currently does not.

2) One of my solutions.

Here's how you do it.

A) Be Essence 3+, with suitable Charms.
B) Find a suitable mortal.
C) With Behemoth Forging Meditation, grant said mortal 6 to 9 points worth of mutations. No more, no less. You can do this in multiple iterations or with an Oneiromancy.
D) Grant your mortal Awakened Essence.
E) You now have a (temporarily) free willed behemoth before you, one that can channel Essence.
F) Tame the behemoth, making it your minion.
G) Grant your new minion a full suite of Graces (Way is optional).
H) Open one of your minion's Graces, making it a full fledged Raksha.
I) Return the new Raksha's Heart to it.
J) Duck the book thrown your way by the GM as you ask what happens to the mutations your former minion once had.
K) Done!


And, of course:

Bone of Contention

There is a tribe of Raksha originating from the cold northern mountains that has proven quite successful at spreading throughout Creation. Large, earthy seeming and often nocturnal, these Warriors find a perverse delight in enraging those they meet and then feed gleefully on the ensuing indignation and bile. When threatened by the forces of the Empire, they retire to underground safeholes, only to return later and resume their old tricks, perhaps wearing a new name. Even when convincingly slain, they often come back later, seemingly unaffected by the smackdown they received.

Growing wise to their tactics, a group of Dragon(blooded) sought to hunt down these foes of civilized discourse into the depths of their Dungeons. There, they faced one of the great Trolls (for such is the name of the Raksha tribe we speak of), which seemed unwilling to fall no matter how hard it was hit. Finally appealing to their sifu, they gained knowledge from beyond the fourth wall, of a troll's purported vulnerability to fire.

So the great foe was cut down once more, its quickly regrowing body sliced and stabbed until the skeleton was revealed, and the full fiery might of the Dragons applied. Little did the servants of her Red Magesty know that to a true troll, flames are a source of strength, vitality and rejuventation.

Thus, though only the creature's Bone remained, it retains great power and is a constant source of meaningless arguments, warping ordinary conversation into vicious insults, and raising topics best left alone for the sheer joy of seeing normal people devolve into yapping rabid fans.

Which side is right and which wrong? The Bone does not care, so long as there is pointless fighting and ill will. Thus far, it has fed more richly than it ever did when alive, and seems set to gorge even further.

1-dot Oneiromancy
Assumption of Dreams and Passion - the Bone is utterly, categorically, and indubitably wrong about anything. Even (especially) when it agrees with you.
Prince and Pauper Approach - anyone else talking about the subject at hand (or any subject, for that matter) is obviously biased and seeking to mislead the innocent public.
Unitary Being Forge - every word, thought, and even syllable pronounced by those who disagree with you conceal vile calumnies about your essentially righteous nature, which must be denied at once and merit the most vicious verbal retaliation. Topic, what topic? Can't you see it's about them saying those unforgiveable things about us?
Heart Stealing Kiss - trying to keep things reasonable when the Bone is nearby is manifestly impossible, and will consume your Temperance before you can even get close to starting the job.

I hope this explains how my methods work