-In my story, my main character comes across an immortal being, chained and isolated under a mountain for countless years; subsequently losing memories from her past over time, while still being conscious and aware of her existence during the aeons.
Question: How long will it take for an immortal to lose all memories/ self-consciousness? Will being conscious affect the rate of memory loss? (Keeping in mind that she does not need basic human needs such as consuming food, water, human company etc.)