Charlemagne's Stirrup

Origin
Charlemagne was King of the Franks, founding an empire that united the Western half of Europe during the Middle Ages and laid the foundations for modern France and Germany. He took the Frankish throne in 768 and became King of Italy from 774. From 800, he became the first Holy Roman Emperor — the first recognized emperor in Western Europe since the fall of the Western Roman Empire three centuries earlier. While Charlemagne already ruled his kingdom without the help of the Pope, recognition from the pontiff granted him divine legitimacy in the eyes of his contemporaries. His ascent to power was marked by nearly unilateral control over incursions into Italy, Spain and Britain. The Carolingian Empire, consisting of the expanded Frankish state, began to falter after his death and division of leadership between his sons.

Effects
Installing Stirrup onto horse's saddle allows whoever is sitting on the horse to control seats of power, but the person must be on top of the horse to keep the artifact activated.