Bloodlines are granted to the descendants of very powerful beings of Saint Rank or Divine Rank. Saint rank bestowal only allows 35% of user bloodline purity and 3-4 abilities that come with it.
Meanwhile, Divine-tier beings can impart 70-90% of their bloodline purity, four to six abilities, and one passive skill. All are random except race-exclusive skills such as the Phoenix that can resurrect after death.
How much depends on the descendants' ability rank and tier.