The destruction of Jakub's Altar has purified March Edge, the sword of Freemarch's Kings. Wielding this symbol before that of Jakub's new master will force a confrontation. Use March Edge before the Idol of Regulos, then kill Jakub the Iron Tyrant.
You have done it. You have destroyed Jakub and released Freemarch from his grasp. The people of Freemarch are forever in your debt!