Making a Rocket?

As the Prana in the blood is used up, the Spirit Container would inject more. It would take some time for the new blood carrying Prana to circulate throughout the body.

This meant there was a limit in the amount of Prana a cultivator or Pranic Beast could draw upon to activate their Primary Nature. They couldn't just use up all their Prana Reserves for one massive attack.

Prana Blood Skill achieved exactly that. By fusing the Spirit Container with the heart, it allowed all his Prana to circulate through his body. It was a dangerous ability.

If he maintained it for a long enough duration, his body would casually explode.

And even after deactivating the Skill, side effects would persist, turning him weak for a significant duration.

His Prana would become unresponsive for a short while and he would feel sluggish. Therefore, it was meant as a trump card to unleash an explosive burst of power.