Final answer:
The most famous quest by medieval knights was the search for the Holy Grail. Knights also participated in the Crusades, a series of religious wars to reclaim the Holy Lands, which were motivated by factors like religious zeal and the promise of adventure and wealth.
Step-by-step explanation:
The most famous quest undertaken by knights during the Middle Ages was the search for the Holy Grail. This quest is deeply rooted in Arthurian legend and Christian mythology, where the Holy Grail is often depicted as the cup used by Jesus at the Last Supper and is said to have miraculous powers. The pursuit of the Grail symbolizes a knight's journey towards spiritual perfection and enlightenment.
Knights of the time were also involved in other quests, such as participating in the Crusades, which were a series of religious wars sanctioned by the Latin Church in the medieval period. The Crusades were military campaigns intended to regain control of the Holy Lands from Muslim rule. Knights took to these crusades for a variety of reasons, including religious zeal, the pursuit of adventure and wealth, and the promise of forgiveness of sins.
Moreover, the quests of medieval knights and the Crusades had significant impacts on the history of the period. The Crusaders' conquests and interactions with other cultures had long-term effects on European and Middle Eastern history, including shifts in power and the spread of ideas.