Short answers, pulled from the story.
Thomas Percy, 7th Earl of Northumberland (1528-1572) was an English Catholic nobleman and rebel leader who led the Rising of the North against Elizabeth I in 1569. He served as a Knight of the Garter and Warden General of the Marches before his rebellion, and was later beatified by the Catholic Church.
Percy and the Earl of Westmorland led the Rising of the North in 1569 to protest the systematic persecution of Catholics under Elizabeth I and to seek the liberation of Mary, Queen of Scots. Rumours of Pope Pius V's approaching excommunication of Elizabeth pushed them into action before their plans were fully formed.
After the Rising of the North failed, Percy fled to Scotland, where he was captured by James Douglas, 4th Earl of Morton, and held at Lochleven Castle. After three years in captivity, he was sold to the English government for two thousand pounds and beheaded on the 22nd of August 1572 at Pavement in York, refusing an offer to spare his life if he renounced Catholicism.
Pope Leo XIII beatified Thomas Percy on the 13th of May 1895. His feast day is observed annually in the Diocese of Hexham and Newcastle on the 14th of November.
The baronies of Percy and Poynings and the older earldom of Northumberland were forfeited due to his treason conviction. The newer earldom of Northumberland created in 1557 was not forfeited, owing to a specific clause in the patent. The earldom passed to his younger brother Henry Percy, who became the 8th Earl of Northumberland.
Mary Percy (the 11th of June 1570-1643) was the daughter of Thomas Percy, 7th Earl of Northumberland, who became a Benedictine nun and founded the Benedictine Dames in Brussels. Nearly all existing houses of Benedictine nuns in England are descended from her foundation.