Invulnerability

Invulnerability reduces all damage taken to 0 and is the only form of damage reduction that affects true damage. Drain effects, such as life steal, will have no effect against invulnerability.
 * (except against her target)
 * (except against her target)

Invulnerability may also refer to, although this only prevents health from being taken below 1 and it does not actually reduce the damage inflicted.