Healers occupy many different types of jobs, such as field nurses, doctors, and surgeons in established hospitals.
The type of magic that healers use is weak, and is only useful for speeding up the body's natural healing process. It can close wounds and stop blood flow, but it cannot remove or regenerate tissue any more than the body can do itself.
Healing magic is unique to this group of angels, as they draw energy through their halos from Heaven itself. It isn't possible to learn by any other means.
Some demons are able to regenerate or heal themselves through magic, but the ability to heal another person has never been recorded in any magic user, demonic or otherwise.
3rd rank healer
3rd rank healers work as nurses, either in established hospitals or as field nurses who join the military on missions. In relation to the military, their primary job is to limit trauma. They rely heavily on healing magic and first aid to do so.
Elsewhere they take care of more typical nurse work, checking up on patients and tending to their basic care. The lowest ranking healer angels have a plain, green halo.
2nd rank healer
This rank of healers can be doctors, head nurses or take care of other medical jobs that require specialization and strong knowledge of medicine.
Since healing magic is only really effective for treating immediate trauma, 2nd rank healers rely just as much on "normal" medical procedures. They bear a glowing, green halo.
1st rank healer
The highest ranking healers are typically specialized surgeons, chief physicians, medical researchers or the like. They have less use for magic and more for an extensive knowledge of medicine.
They have glowing, green halos with sun cross symbols on them. The halo also colors their wings in shades from green to blue.