Paeul is a famous, learned and powerful Necromancer of Philosophia, though one that doesn’t use his magically gained influence for politics, which he (quite unusually) tries to stay out of. He’s the adoptive father of Valeira, whom he took off the streets as an urchin. While he tried to keep her out of the dangers of his magic, she ended up learning from watching him and reading his books anyways.
Paeul’s necromantic practice is sought after because he might know something that circumvents or lightens the Diamond Crisis. After he was imprisoned for causing an accident, Jade the Just gave him clemency in exchange for his services, in secret.