C3571 The Ten Strength Angels

According to the legends, the body of an angel cannot leave 'heaven' for too long, or else it will be contaminated by the world's foul energy, and the soul will no longer be pure.

If an angel wanted to descend into the world for a long period of time, then they would need to possess a 'vessel'.

The Holy Cross Church believed that an angel was a 'pure body', and could not possess any biology