He was shown to be a dedicated knight along with his five main relatives who joined the Knights Templars. He was also a caring father of his two children and when he found out that they're missing, he was determined to search for them.
The countess tells George Stobbart that the curse in de Vasconcellos' family started during the raid of the Inquisition. Don Carlos retired from being a Knight Templar and became a scholar. While he was away for his scholarly journeys, the Inquisition arrived to destroy the de Vasconcellos' Knights Templar. When Don Carlos returned, he found out that his children were gone and his loyal manservant killed during the raid. He was mad with grief because of the loss of his children. He took his armor, sword and shield and rode out alone. He was never seen again after that.
George managed to solve the chess puzzle in de Vasconcellos mausoleum and discovered a chalice hidden on the wall. The countess is happy and realized that the Knights Templar never betrayed the de Vasconcellos by hiding a secret artifact. She decided to give the chalice to George and then George promises to the countess that he'll search the tomb of de Vasconcellos.
George discovers the tomb of Don Carlos laid in Montfauçon church. The tomb implied that Don Carlos failed his search and died in France. George sees the pegasus symbol that matches the one in the chalice. The tomb also has biblical references which leads to the old well in de Vasconcellos' house and then the truth regarding to Don Carlos' missing children.
- Don Carlos was one of the six knights of the de Vasconcellos family who joined in Knights Templar.