Matriarch

The Matriarch is a title for the sole Harpy who rules the territory of Harpy's Reach. She answers only to King Lucan. Her rule is aided by the heads of the five clans (see Harpy for more detail) who call themselves a 'high lady.'
A Matriarch can only rule for five centuries according to a tradition that was written into law soon after Harpy's Reach was gifted to them. This tradition states that after five hundred years of rule, the title of Matriarch is handed down to the oldest heir of the previous Matriarch. If there is no heir (and this happens more often than not due to the low fertility of all immortal beings), then the title is passed to the next most powerful high lady of the five clans. 
Any Matriarch can be challenged for their position if there is a high lady (or family thereof) that do not believe they are powerful enough to hold it, but it is considered incredibly taboo to issue a challenge in the first century of rule.