Invulnerability is the power to be immune to conventional harm.
Characters with such powers may simply be unaffected by normal attacks, necessitating the use of things like
Durability Negation to get through.
Others have more conditional invulnerability, such as one that just prevents harm from conventional weaponry, but can be easily circumvented by supernatural abilities. It can be considered the defensive equivalent of Durability Negation, negating simple Attack Potency, though one should be careful not to apply
No Limits Fallacy.
These guys are pretty much invulnerable until you break their wings which fits 1:1 to the page description of invulnerability