During this period, Wang Xian had gained some understanding of his essence blood; blood of the Divine Dragon.
The essence blood was able to assimilate the bloodlines of most living organisms.
But it also had a limitation. It was unable to assimilate bloodlines with a grade higher than itself, or those coming from an organism with stronger powers.
Amongst all living organisms, the bloodline of the Divine Dragon was considered as the apex. Yet, as the current abilities of Wang Xian were still too weak, the energy stored in his essence blood remained low.
Hence, the attempt to replace bloodlines of a relatively high grade would impose some difficulty.
As for the experts whose abilities far supersede Wang Xian's, not only would his essence blood be unable to evolve the party's bloodline, it would be absorbed by the party for energy intake.