The abbot of the abbey where Aria Wren spent some time and become a cleric of the Unnamed One. Father Jacob asked Aria Wren to go on her first mission for the Raven Guard which is where the first fragment of the God Killer Blade was discovered along with Sabine Wren.
Father Jacob believed that Aria Wren has been chosen by the Unnamed One for a higher purpose due to the speed with which she unlocked her divine gifts and the proficiency with which she wielded them.
Though he has stepped down from the position, Father Jacob was once Hierophant of the Church of the Five and prior to that served as the High Priest in the Church of the Unnamed One.
It was eventually discovered that Father Jacob was knowingly worshipping and working for Enyalius and was trying to indoctrinate Aria Wren since her ancestry made her a perfect host vessel; when it became clear that Aria was lost to them, Enyalius took Jacob as a temporary host instead.
As host, Jacob was slain in the final battle against Enyalius, killed with the God Killer Blade.