The legendary artifact in Greek lore that granted immense power was the Golden Fleece. This treasured item belonged to the ram that saved Phrixus and was sought by Jason and the Argonauts. It embodies themes of heroism and quest, symbolizing authority and kingship in ancient Greek society. The Golden Fleece's pursuit led to numerous adventures and trials, underscoring the importance of valor and the lengths to which heroes would go to achieve their goals. Its enduring legacy continues to inspire stories about heroes and their quests for greatness.