From SuspireWiki

The title of Rex Nemorenis is the least used title in the entire Circle of the Crone. In fact it's said that very few Crones have ever heard of the King of the Grove in modern nights. The title was held by an elder Acolyte who, from her haven (which was typically so far removed from the populance that the Rex Nemorenis could be called a hermit) would keep the secret knowledge of the Circle, not only of the individual Acolytes but also of rituals both current and those considered anathema. Because of the range of knowledge the Rex Nemornis would council Acoyltes, sometimes shifting the entire direction of the cult with a few subtle words.

Though there are no known Acolytes serving as Rex Nemorenis it's rumored that there are still some hidden away in the wilderness, watching their domains.