Who is Count Volkmar from The Source; a Novel and what is their importance?

Volkmar is the Count of Gretz in Germany. He refuses to join a group loyal to the false Pope but helps form a Crusades group through his brother-in-law Gunter's promptings. The object is money but they slaughter many Christians and Jews. His wife and daughter are killed along the way. In Makor he is injured and his leg is amputated. He remains there and remarries. When Gunter, his bother-in-law returns to Makor, he builds the castle, Ma Coeur.