St George, Martyr - 23 Apr

He was martyred at Lydda (now in Israel) in about 303, during the persecution of Diocletian. Like so many saints of that period, the only fact that we can be certain of is his martyrdom. His cult spread quickly through both the East and the West, and the legend of St George and the Dragon only appeared some time afterwards.
  During the crusades, George was seen to personify the ideals of Christian chivalry, and he was adopted as the patron saint of several city states and countries, including England and Catalonia. King Richard I of England placed his crusading army under the protection of St George, and in 1222 his feast was proclaimed a holiday.  (universalis.com)

St Adalbert of Prague, Martyr - 23 Apr

St Adalbert of Prague 956-997.  He became bishop of Prague in 983. He met with intense opposition from the nobility. He withdrew to Rome but was sent back to his diocese by Pope John XV. He encouraged the evangelization of the Magyars, and founded the great abbey of Brevnov, but the opposition continued and he was at length forced into exile. He went as a missionary to Pomerania to preach the Gospel to the heathen Prussians, and it was there that he was martyred at the age of 41.  (universalis.com)

St Fidelis of Sigmaringen, Priest & Martyr- 24 Apr

St Fidelis 1578 – 1622.  He was born in Sigmaringen in Germany. He joined the Capuchin Friars at the age of 35 and led a harsh life of prayer and vigils. An assiduous preacher, he was ordered by the Congregation for the Propagation of the Faith to preach orthodox doctrine in the Grisons (part of Switzerland). He was murdered by a Calvinist mob at Seewis on 24 April 1622.  (universalis.com)

St Mark, Evangelist - 25 Apr

He was a cousin of Barnabas and accompanied the apostle Paul on his first missionary journey; later he followed him to Rome. He was a disciple of Peter, and his gospel is told from Peter’s point of view. He is credited with founding the Church in Alexandria. His body was stolen from Alexandria in 828 (though some say that the wrong bones were stolen) and taken to Venice, which adopted him as its patron saint.   (universalis.com)