Instincts
Sargun stood up and raised his sword above his head with both of his hands. He clutched it tightly and began to imbue his energy into it.
This was going to be his last attack, and that's why he poured everything he had left, every single ounce of strength, into this one last attack.
It was true that before Master Rank, you couldn't use energy outside of your body freely. But there were some cheats or rather loopholes you could use.
Like using a weapon or a staff as a medium for the transfer of energy.
Sargun gritted his teeth as he felt fatigue washing over him. Even though the battle was short, he exhausted himself by going over his limits. Adding the depletion of his energy reserves, it was bound to happen.
Sargun knew of that and continued to imbue the energy in the sword until he had depleted most of it.