What remains of the The Saqalu were once among the noblest beings in our world. ... – I’ll let that article give you description of power and appearance.
Regarding the Broken, here are Notte’s own words:
They still wield the awesome power they always did, but they are no longer… stable.
A Broken Guardian is as likely to take your life as she is to save it – for if you are dead, you are no longer in danger.
I only know of a few now living, and while I may call one or two “friend,” I have no faith this will translate on to anything with my family.
If you see one, run.
If you see one, leave as quickly as possible.
He will sense your threat toward the humans around you. He will know you pose a danger, and he will kill you.
Worse, he will know that you are in danger from germs, wounds, sorrow… and he will act.
All that you can do is run.