OBJECT_INVALID is an object-valued NWScript constant indicating that no object has been specified. This value can be thought of as meaning "none", as it is commonly used by functions that return objects to indicate that there is no object to return. An object-valued variable can contain an invalid object, yet not contain the value OBJECT_INVALID. This is most often caused by the variable referring to an object that has been destroyed or to a player character that has logged out. In order to detect this situation, use GetIsObjectValid() instead of comparing the variable to OBJECT_INVALID.