Day 148 - 1:22 AM - Mountain Sanctuary, Catanduanes
Bloodline. It was an idiomatic way of to refer a family history and ancestry and genetic heritage. It could also pertain to one's Lineage.
To most modern common people, the term itself was not widely used, as such, irrelevant.
However, to people of the hidden side of the world, it was a very important word.
After all, it could dictate the capabilities of a person.
Some families had unique traits that could only be passed on to their children. To families of magicians and cultivators, it could either be a talent or a trait.
In the case of Mark's family, one of Mark's ancestors might have been a pureblood that managed to escape the culling of the Blood Demon race.