In the wake of The Ancestral Tree's corruption at the hands of Vaedrin, one of the Light's greatest wardens became one of its greatest foes.
Before the Wars
There are not many details recorded about the Circle of the Ancestors prior to the Cataclysm Wars. The Circle, whilst always respected, had fallen somewhat into obscurity across the centuries before Council's rise to power. Thanoth was born within the Circle's community, that much is known.
During the Wars
It took a few months before The Dark Council turned its attention towards The Ancestral Tree. The Council, with Vaedrin's forces, kept the Circle engaged in minor skirmishes in the early stages of the War. Although the continent, as a whole, was largely unaware of the Circle's importance, The Dark Council did not share that ignorance. The Ancestral Elder, Thanoth 'Nightcarver' Gathakanaki soon made his presence known. Those that witnessed him in action would suggest that Thanoth was one of the most gifted druids to have ever lived. However, given the relative anonymity prior to the Wars, there are arguments that his strong bond with the Ancestral Tree may have allowed him to tap into more powerful magic.
The day finally came when Vaedrin and the Council decided to take the Ancestral Tree once and for all. Those early skirmishes proving to have only been scouting attempts for the real assault that came months later. The vast numbers of undead that Vaedrin had managed to accumulated proved too much for the Circle's defences and Vaedrin successfully managed to corrupt the Tree with his Blight. The innate power of the Tree never allowed Vaedrin's Blight
to take over fully, but the damage was done. The Tree was corrupted and the bond that connected the Tree with the Circle, unfortunately, worked against them. Darkness took the souls of the Circle of the Ancestors. Thanoth, the Ancestral Elder, had the strongest connection of all, which left Thanoth the most affected too.
The Archdruid of Agony
Thanoth's corruption was so absolute that, along with his druidic talents, it earned him a space on the Council. He was the last of Circle of Nine to join. Thanoth became an instrument of much suffering. His connections to the Blight and druidic talent meant that he was especially capable of casting the same infliction that Vaedrin had cast upon the Ancestral Tree. The Blight that persists in what is now known as the Blightlands was the work of Vaedrin, but the Twisted Forest in the Elven lands, that was caused by Thanoth.
Even though the Ancestral Tree was eventually cleansed of Vaedrin's work and the rest of the Circle returned to the light, Thanoth's corruption was so absolute, he was still a servant of Darkness until the end. Thanoth died alongside the rest of the Nine during the Siege of Arkran. It was noted that the last to have joined the Nine was also the first to have fallen in that battle. Losing one of the people capable of turning the Light's forces back against them was a pivotal moment in the eventual loss the Nine suffered in that final conflict. It is also suggested that Thanoth should have been capable of avoiding or deflecting the fireball that consumed him. Theories consider the potentiality that at that moment, the good in Thanoth allowed it to happen.