In life, Don Sidonia had been the commander-in-chief who lost the Spanish Armada to the English, due to his own lack of initiative and self-confidence, but in no small part the failure of the fleet had been found in a direct order given by King Philip II of Spain. Hence, the Lasombra elders decided to use the Admiral as an object lesson to the king.
Sidonia was Embraced and presented in a starved state before King Philip II, the slender hand of the creature's sire the only thing holding him back. For the next six hours, Doña Beatriz proceeded to calmly explain the basics on strategy and leadership to the frightened monarch, while the former Admiral howled for blood the entire time.
Doña Beatriz and her peers originally planned to destroy the Admiral right after the lesson was over, but the Doña felt guilt for using a Spaniard of noble blood in such a manner. She then decided to spare him, and gave the Don a proper training in the ways of the Clan and also in the ways of the Sabbat.
In his unlife, the former duke of Medina Sidonia quickly proved himself a brilliant tactician, determined to erase the shame from his defeat in the Channel. His great success as a Lasombra granted his sire ascension into the ranks of Les Amies Noir and himself great prestige for war efforts coordinated by him from New York to Manila.
The Don has maintained his hatred against Britain and strives to see its destruction. He also has a grudge against a Ventrue named Parma, who was a former mercenary who deserted the Armada and joined the British.
For the historical person, see Alonso Pérez de Guzmán, 7th Duke of Medina Sidonia.