Strategic Advisor and Deputy: As a close advisor to the Grand Master, the Grand Seneschal played a significant role in the order's decision-making processes. Their counsel would have been sought on matters of policy, strategy, and relations with secular and ecclesiastical powers. In the frequent absences of the Grand Master, whether due to travel, illness, or death, the Grand Seneschal would assume full command of the order, wielding the authority of the highest office.

Military and Logistical Command: While the Marshal was primarily responsible for the direct oversight of military matters, the Grand Seneschal also held significant martial authority. They were often involved in the planning and execution of military campaigns. In times of war, the Seneschal's logistical prowess was paramount, as they were responsible for ensuring the supply of troops, horses, and provisions for the Templar armies in the field. On the battlefield, the Grand Seneschal could be found leading contingents of knights and, in the Grand Master's absence, would command the entire Templar force.

The combination of these extensive administrative, advisory, and military duties made the Grand Seneschal an indispensable figure within the Knights Templar. Their ability to effectively manage the order's vast resources while also providing capable leadership was fundamental to the Templars' success and influence for nearly two centuries.