The method to fuse all 9 Spirit Flames into one was quite simple.
All Tang Yin had to do was bring his first Spirit Flame into the eye of the Heaven Devouring Abyss's vortex. Then with the aid of the Heaven Devouring Abyss, he would need to incorporate each Spirit Flame into the first Spirit Flame separately.
Tang Yin took a deep breath before starting the process. He controlled the first abyssal black Spirit Flame to enter the eye of the black vortex which crackled with black and red lightning, the Heaven Devouring Abyss.
There were no changes, the first Spirit Flame remained stationary inside the Heaven Devouring Abyss.
Tang Yin moved his gaze onto the second Spirit Flame. Similar to the first, he controlled the second Spirit Flame to enter the Heaven Devouring Abyss.
He did not keep it stationary, instead, he made it collide directly with the first Spirit Flame.