The Spirit Pagoda's deputy Pagoda Master Zhang Geyang's family had always held high-ranking positions in the Spirit Pagoda. Hence, when he was still young, his family had gone through a lot of trouble to find this spirit soul for him to merge with as his first spirit soul.
For ordinary soul masters, the number of spirit souls obtained would increase with the improvement in their cultivation bases. Naturally, the spirit souls obtained during the later stages of their cultivation would be more powerful. For top-grade soul masters, their first spirit soul would be the one they spent the most time with. Once the spirit soul reached a certain growth, it would improve alongside the soul master. These spirit souls were the ones that soul masters liked the most. They were also known as companion spirit souls.
For example, Zhang Geyang's spirit soul was the same as his martial soul. It was also his companion spirit soul, the Hell Flame Beast.