In the world of magi, birds are treated as “the carriers of souls”. Setting his biased thinking aside, Gransurg, who made birds the foundation of his thaumaturgy, was an excellent soul carrier.
But. That bias caught the attention of the Crimson Moon. He challenged Gransurg to a battle for fun and defeated him.
Gransurg, who was an average magus and had no special blood or outstanding factors was killed immediately ---- or he would have, if not for a coincidence that saved him at the very last moment.
The Crimson Moon let the coincidence be and let Gransurg go. Instead of using him as a blood pack (Dead Apostle), he ordered Gransurg to live as his personal magus from then on.

Character Material - Gransurg Blackmore