The strength of the Tantra Sect was by no means much weaker than the Buddhism of the Dahua Heavenly Dynasty.
If the Seven Immortals Alliance is considered the premier force of cultivators in Da Hua, then the Tantra Sect is the one that ranks second.
The cultivators of the Tantra Sect possessed a very special method of reincarnation and cultivation, allowing them to retain most of their cultivation from their previous life into the next. With accumulations over successive generations, the Tantra Sect was replete with powerful individuals, especially among the Earthly Immortals, where they likely outnumbered those of the Seven Immortals Alliance.
Therefore, even the Seven Immortals Alliance found it difficult to intervene in the affairs of the Tantra Sect.
