Bloodline members are ageless and immortal, yet it is very difficult for them to increase their strength.
However, "very difficult" does not mean "impossible." By comprehending the Bloodline Resonance, members of the Bloodline can still slowly augment their power until they reach the limit of their own bloodline.
Of course, this process is incredibly slow, even when delving into the most suitable deep slumber for comprehending the Bloodline Resonance, the time required is often measured in years.
Dark, Wildness, Blood and Flesh, Spirit, Observation...
These five major directions of Bloodline Resonance represent the five paths of advancement for the Bloodline, and any breakthrough in one direction of Bloodline Resonance means that the members can progress even further.
