Scepter of Truth
The Scepter of Truth was needed during a time when the royal line of the Kingdom of Dalriada wasn't certain who was actually of the blood.
Created hastily at the request of the King, no other functions were built into the scepter; if someone not of the royal family line touches the scepter they will feel intense pain, pain enough that they can no longer hide that they are clearly a usurper.