Vin's mother's earring

Vin's mother's earring, a seemingly innocuous piece of jewelry passed down from her mother Reen, emerges as a pivotal plot device in the Mistborn Era One trilogy. Initially worn by Vin as a memento of her troubled past, it is revealed in 'The Well of Ascension' to be a malevolent hemalurgic spike harboring Ruin, the god of destruction. This allows Ruin to subtly influence Vin throughout the series, culminating in her critical realization during the cataclysmic events of 'The Hero of Ages,' where she removes it to break free from the god's control and fulfill her destiny.