Each artifact represents an element of friendship and only activates if the wielder possesses the corresponding trait and if all six are used in conjunction. They have been wielded on rare occasions, particularly during events marked by danger and anarchy as a last resort to restore and enforce the balance of peace and order. However, the effects of their use are generally temporary and non-lethal, usually a form of banishment or imprisonment.
These artifacts were once wielded by Celestia and Luna, needing the elements from the Tree of Harmony in order to defeat Discord, who at the time ruled over Equestria with little competition, if at all. Upon Nightmare Moon's defeat, Celestia herself wielded the Elements, and eventually sealed them away inside the Castle of the Two Sisters. It wasn't until the Mane Six came together to defeat Nightmare Moon again did the Elements of Harmony became used once more.
These items were also used against Discord on his return to turn him back into stone, and used again to remove him of his stone prison to reform him.
Before the Mane Six left off for Homeworld, Celestia had Twilight sparkle keep the elements of harmony with her for safe-keeping, as they would be safer staying with her rather than on another planet.