Paint the scene in your head. In a long corridor riddled with flames and falling debris from the ceiling. At one edge of the corridor stood Kyle Trueblood, dressed in sharp costly robes, adorned with jewels and ornaments of different kinds. Amongst the people here he stood out for the wealth worn on his body.
Meanwhile at the other end was a young boy of barely fifteen, standing amid countless darkish purple beings which have a striking resemblance to specific beings. These undead beasts lack real bodies and are purely made of mana. This aspect practically gives them an immortal body. This is something any strong necromancer could wish for and only the best of them all can reach something close to this level!
Only, one forbidden magic can make the other dark arts look like child's play, including blood magic.
Outside those who have a strong relationship with the blood clan, no one else should have blood magic unless they are the guardians and pioneers of the dark arts.