How would you create this creature? (Monster from a dream I had, lol)

[MonkeySage]

So, just moments ago I woke up from a dream. In this dream, there was a monster that could appear variably as either the shadow of a child, or the shadow of a murder of crows. The creature wasn't evil, but had a pretty alien sense of morality. It feeds mostly on small animals, but goes for larger prey when possible, and in child form it is intelligent and capable of speech. It's actually sort of friendly, if it judges you not to be a threat. It doesn't normally attack unprovoked, but when forced to defend itself it takes the latter form.

It's... not a shadow in the sense of undead, but it is extraplanar. In my dream, it came from purgatory, so I'd guess it has some association with death. It may not be evil, but it definitely doesn't belong in the material plane.

It's presence is announced by the lack of sounds from nature: No birds singing, no crickets chirping, no frogs, etc.

EDIT: Just realized this probably belongs in the homebrew forums. Can a mod move it?

[Bohandas]

was it bound to move along surfaces like a real shadow?

Also the sign of its presence sounds like the Unnatural Aura ability, or perhaps a sleep or silence based equivalent thereof
Unnatural Aura (Su)
Animals can sense the unnatural presence of a caller in darkness. Any animal within 30 feet must make a DC 17 Will save or become panicked until it is no longer within 30 feet of the caller in darkness. A panicked creature that is cornered begins cowering. The save DC is Charisma-based

Unnatural Aura (Su)
Animals, whether wild or domesticated, can sense the unnatural presence of a spectre at a distance of 30 feet. They do not willingly approach nearer than that and panic if forced to do so; they remain panicked as long as they are within that range.

[MonkeySage]

It moved freely, like a ghost. :)