This was the underworld identity of Christopher Chant's uncle Ralph Argent, a thoroughly nasty character who manipulated young Christopher into spirit traveling for him and help0ing to transfer illegal magical goods such as mermaid body parts and dragon's blood into his own world where he could sell these items for a huge profit.  The Wraith and his gang were eventually caught and put out of business by Christomanci Gabriel de Witt and his agents, after a tough battle.