The "Lady of the Mercians" refers to Aethelflaed, a prominent historical figure in early medieval England. She was the daughter of Alfred the Great and became the ruler of the kingdom of Mercia after her husband's death. Aethelflaed played a crucial role in defending her kingdom against Viking invasions and was known for her military leadership and strategic fortifications. Aethelflaed's reign lasted from 911 until her death in 918. She is celebrated for her efforts in uniting the Anglo-Saxon kingdoms against common threats. Her legacy includes the establishment of several fortified towns, known as "burhs," which helped secure the region and promote trade and stability.