Tollerath
Tollerath was the only one of the Jade Tower's Chronomancers to survive the Scarlet War. He lived in secret for centuries, and was one of the founders of Haven. He also designed the wards and spells that hide the city from scrutiny and protect it from attack.
When he met the Companions of the Rising Sun, he was undead, product of the Bone Lord's Totentanz gate. The Bone Lord had not perfected the gate's design when Tollerath was forced through it, and though it left his intellect intact, it stripped him of his connection to both the Arcane and Divine Source.
According to the Amber Dragon, who sent the Companions on a rescue mission after him, Tollerath was the only one who knew how to undo the Mt. Daneasus wards; the rest of the Chronomancers were required to be in the Temple itself to complete the binding.
Interestingly, though primarily an Arcane spellcaster, Tollerath had a few (much neglected) levels in cleric (dedicated to Mehana).
Tollerath taught the Companions what they would need to know to unbind the wards on the Holy Temple, and was one of three links in the chain required to accomplish this massive magical feat. See Glory Exultation for more detail.
At the end of that effort, his connection to life, or undeath, was tapped out by the great exertion, and he lingered only long enough to see his lover, Aurora the Insightful one last time, before departing to the Valley of the Magi, the last resting place of the Arcanists. It is assumed he went to rest there, and will be seen no more.
He is survived by his son, Tollerath the Younger, known to the Companions as TJ.