The bloodline essence extraction technique was a well-developed technique, but it was not a successful one. It could extract the bloodline power from beasts, but it could only extract the current strength, not the overall potential.
In other words, once this bloodline essence was injected, it could quickly rise to the strength of the beast. However, if one wanted to break through, they either had to use the bloodline of a beast with the same race but stronger, or use the bloodline of a higher race. Of course, the strength of the beast had to be higher than the previous beast.
