The circle of protection created by the wings of the Broken. Nothing harmful can penetrate it; four-winged Guardians have been known to keep their charges alive and well in water, under spell-attack, in the middle of fires, and under hail of bullets.
Anything that attacks that simply ceases to be when touching the caim. It’s theorized the Guardian wings actually generate an invisible portal to some unknown dimension, where all the bad stuff just goes, negating pesky things like transfer of energy. Of course, that doesn’t explain how some things ricochet, but that’s yet another mystery.