What ability is this?

[ByArrow]

The character has mystical protection. If someone attacks the character while her is asleep, for example with a knife or dagger, the knife and dagger will shatter and the character will suffer no harm. Normally, the character can be harmed by sharp objects such as knives and daggers.

So what ability is this, How should I index this?

 

[Setsuna_tenma]

invulnerability

 

[Random-Helper323]

It sounds like limited invulnerability, but does this only apply to weapons? You describe the weapon shattering.