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 not a small part for the failure of the fleet had been found in the order of King Philip II of Spain, so several Lasombra elders decided to use the admiral as an object lesson to the king.
He was Embraced and presented in a near-starved state before the Philip II, while his sire held him back and and explained the basics of leadership to the frightened king while the former duke of Medina Sidonia howled for blood. Several elders of the Clan wanted to kill the don afterwards, but his sire intervened, feeling pity for him and instructed him in the ways of the Clan and the Sabbat.
In 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 against New York and 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.