Jakub is the target in the latest adventure through Rift from Trion Worlds

Now onto the Iron Fortress and Jakub the Liar. I’m to destroy four altars sitting high atop the corner towers inside the fortress itself (the altars - the Altar of Sacrifice, the Altar of the Despoiled, the Altar of the Walking Dead, and Jakub's Altar, are the objects that give Jakub his power). It takes time to accomplish this as it means fighting your way through the Endless Cultists patrolling the walls.

After fighting through them all and finally destroying Jakub’s altar I pick up an ancient sword resting upon the plinth. Apparently it is something of a symbol of power in Freemarch. When I  return it to Denegar’s Stand there is much rejoicing. “Jakub's Altar is destroyed, and its evil no longer binds the March Edge. For centuries, the sword was wielded by the kings of Freemarch as a symbol of justice, until Jakub's malevolence corrupted the blade. Your actions have restored the weapon to its former purity.”

While exploring the castle, a new quest presents itself. A book I find in one of the rooms turns out to be a discourse on planar entities that describes how to summon a demon called Legul. To do this I have to place nine corrupted skulls (taken from the bodies of Endless Court cultists), inside something called the Brazier of Torment (this has to be done to prevent Jakub from allying himself with the demon and increasing his power further).