Between nations, there is no friendship, for a state collective, a small and weak neighbor is considered a good neighbor. This principle also applies to alliances between immortal cultivation sects.
Two sects may support each other, with relationships that can even become closer than that of fellow sect disciples. However, when addressing each other, they always use the term "fellow daoist."
This in itself is something worth pondering.
Thus, this can only mean that these two sects currently have a common enemy and shared interests.
As to who the enemy is, Tan Shuchang couldn't guess.
Because his cultivation level had not yet reached such heights, after all, both of these immortal cultivation sects have histories of great antiquity. Whoever could force these two sects to this point, must at the very least be an almost Immortal-like figure.
However, the shared interests were not difficult to guess.