The Halaku, or crow hosts, are part-flesh spiritual beings formed from the fragments of a once-powerful crow spirit. Like all the Hosts, they seek to gather together with others of their kind to grow and become stronger, but they differ significantly in their methods and goals.
Unlike other shartha, the Halaku are able to possess humans not by physically entering their bodies, but by pecking out a victim's eyes and controlling the body from afar like a puppet, seeing through the empty sockets. This seems to suit the Halaku's purpose, a more peaceful agenda than that of other Hosts: to observe the world, gathering and storing information (though to what end, no-one knows).
This difference in motive may explain why the Halaku are unique amongst the Hosts in that their relationship with the Uratha is not directly antagonistic. Uratha and Halaku co-exist more or less peacefully; neither hates or fears the other, and they generally stay out of each other's way, though the Halaku are known to simply stand back and observe Uratha activities as they observe so much else from a safe distance.