Invulnerability

Invulnerable is a term used to describe enemies who are meant to be invincible. These enemies cannot have skills used against them, cannot be attacked, do not take damage, and do not suffer from degeneration. If you attempt to attack them or use a skill on them, an error message will be displayed saying "You cannot attack. (Invulnerability)". They can be affected by conditions and do lose health due to Life stealing. However, the only way to affect them is with Traps and Area of Effect skills. Skills used directly against Invulnerable creatures don't even activate, and thus cost no energy cost and do not recharge.

NPC Reactions to Invulnerable creatures
Pets:
 * If a pet is targeted to attack them, it will run up and stand still in front of them.

Henchmen:
 * Henchmen will run to their standard attack range, then stand still. They will shout battle quotes, and act as if they were under attack, using defensive skills on each other.

Heroes:

Minions:
 * Minions will run to, and attack the enemy, and will not stop attacking until the minions themselves are killed. It is impossible to redirect the minions' target.

Enemies:
 * Enemies will freeze up and not run away from Invulnerable allies.

List of Invulnerable creatures

 * Oink in Gates of Kryta.
 * Captain Calhaan in The Great Northern Wall
 * Shiro Tagachi in Sunjiang District.
 * Vengeful Aatxes (until their group's Keeper of Souls is destroyed) during the Underworld quest Unwanted Guests.
 * Base Defenders in Alliance Battle.
 * Nian during the quest The Big Bang. (Avaible during the Canthan New Year).

Conditions which affect Invulnerable creatures

 * Blind
 * Weakness
 * Cripple