Not to go too crazy on sizing up enemies as reagents, but it's worth noting that "master mages" are a category of entity that qualify as splendor fuel, and the dot to power scale reserves the first 2 levels for things that aren't personally notorious.
Shape shifting like this is pretty significant magically speaking, as is whatever else this guy had to be able to do in order to survive the Naagloshii's training camp. I'd bet he qualifies for a 1 dot working.
The most immediately valuable use of that is to make a jade talisman equivalent for Lydia. Not need to screw around with researching how to do it, we can make one that has infinite charge in exchange for being limited to when you satisfy your nature as an entry level project post crafting charm.
Even better, we can sync it up with her native powers in a very convenient way.
Form of Primal Nature (1 pt. Form Element)
The Splendor takes the form of something that is primitive, crude, bestial, or a beast. Items tend to be natural objects like rocks and branches, or are crudely-worked, or are decorated with beast- motifs. More often, the Splendor is literally a living animal. This Element defines the Splendor's physical form and gives it a character, and that character is aligned with the feral, primitive, and bestial. Other Elements may draw upon this fact.
While animal-form Splendors are never hostile to their owner, they do not obey that individual as a servant. Instead they will follow their normal instincts and habits, or else act according to some particular pattern of behavior established when the Splendor is designed. If the Splendor is an Adornment, it may be designed so that its blessings benefit the animal rather than the Exalt. Taking a second characteristic Form makes it possible for an Adornment to take the shape of both a beast and an item used by its owner, and to give its benefits to both of them.
Essence element for reference:
Essence-Stoking Spirit (3 pt. Root Element)
This Element can only be part of an Adornment.
The Splendor stokes the fires of the Exalt's Essence whenever she affirms her innermost self. When she regains Willpower from fulfilling her Nature, she also refills her Essence pool.
A dog is a valid shape for this thing to take, and it should basically vanish when not deployed but still maintain a continuous existence.
Which arguably means she should be able to apply her animal boosting charms to it, creating a buffed up minion she can smuggle around and that will refill her essence pool as many times as she can arrange to fulfill her nature.
It's even appropriate for the type of subject we have here, given the animal theme of a their powers.
If we could also somehow build the dog form as an emanation as well that'd be even better.
I don't know what the special advantages from the gods and monsters book are, but stacking them on top of say a 3 dot arcana that's built for murder sounds like a grand old time.
If the guy is somehow worth 2 dots it gets even better. It's just one more point, but the mystic options have lots of potential.
One easy one is this:
Ode to the Incurious (1 pt. Mystic Element)
This Element can only be part of a Fascination.
The Splendor causes anyone who falls under its sway to become utterly incurious about something defined when the Splendor is summoned. If the Splendor doesn't contain a condition under which the target may escape this blasé state of mind, or the target fails to satisfy that condition, then they escape from its influence after one day for a 1-2 dot Splendor, one week for a 3-dot Splendor, one month for a 4-dot Splendor, and one year for a 5-dot Splendor.
Set permanently to "the presence of this dog" so that she can take it anywhere without issue.
A funnier one is this:
Unthinkable Ward (1 pt. Mystic Element)
The Splendor is shrouded in a psychic ward that makes it unthinkable to even consider harming it in any way. Anyone attempting to do so must succeed at a Willpower roll against difficulty (4 + Splendor's rating) and then spend a Willpower point on each turn in which they attempt to do harm to the Splendor.
The roll isn't bad, but you still need to spend willpower to hurt it every turn you try to do so even when you succeed.
I also suspect resisting the effect using mental defenses is probably difficult, considering where it's coming from. Probably something close to perfect or bust.
Note that it says nothing about the aggressiveness of the splendor; it can do what it likes. Since some of these things will very obviously kill you just doing their normal routine it's not even that out of line.
Popping out a monster dog that you need to spend willpower to attack even while it's peeling off your face is a pretty good trick even for an exalt.