Final answer:
The Lady of Shalott is not from Arthurian legend but Tennyson's poem. She creates her quest out of a desire for authentic human engagement and experiences the real world when she sees Sir Lancelot.
Step-by-step explanation:
The 'old Lady' of the castle is known as The Lady of Shalott. In Arthurian legend, although she doesn't appear in the original canon, she is connected through Tennyson's adaptation of the lore surrounding King Arthur and Camelot. The Lady of Shalott lives in isolation under a mysterious curse that forbids her from looking directly at Camelot. Her life revolves around weaving a tapestry depicting the world as seen in the reflection of a mirror.
Her motivation for creating her quest, ultimately leading her to leave her loom and look upon Camelot, arises from her desire for genuine human experience and connection, rather than just observing life indirectly.
This yearning is particularly accentuated upon seeing Sir Lancelot, leading to her tragic demise as she attempts to integrate into the world she has been separated from.