April 5 is the feast of St. Vincent Ferrer, who is an interesting saint, since he was a firm supporter of an antipope. In 1378 a succession dispute broke out for the Papacy. The Papacy had been located at Avignon for quite some time at this point, but a strong popular push (as in, danger of widespread riots) had made the Cardinals feel it necessary to return the papacy to Rome, thus leading to the election of Urban VI. Urban turned out to be a rather unpleasant man, though, and, exasperated, most of the Cardinals left Rome and, despite the fact that Urban had been legitimately elected and was still there, elected Clement VII. Yes, geniuses that they were, the Cardinals tried to elect two men Pope, thus causing the worst crisis in Christendom to that point, and arguably ever. There had been antipopes before, but they were put forward by factions; never before had the College of Cardinals itself actually put an antipope forward. Since Urban was in possession in Rome, Clement went back to Avignon. The Avignon Papacy, as such, had been a somewhat unfortunate episode, but the New Avignon Papacy, as we might call it, weakened the Church by splitting allegiances, guaranteed the spread of corruptions and abuses, and caused no end of confusion among the faithful. It also caused an international crisis, since the French and Spanish kingdoms and their allies recognized Clement as legitimate and the rest of Europe recognized Urban as legitimate. It became even worse in that rival factions in kingdoms with shaky succession laws attempted to manipulate the division to their advantage, supporting whichever one would recognize their claim. And there was no obvious end in sight: after Clement died in 1389, Benedict XIII was elected by the Avignon cardinals, and after Urban died in 1394, Boniface IX was elected by the cardinals still loyal to Rome.
Ferrer and his family, being half Scottish and half Spanish, were supporters of Benedict XIII, and all of Ferrer's preaching was done under Avignon authority. Castile, which which Ferrer became associated, would eventually withdraw support from Benedict XIII due to the Council of Constance in 1414 (at which point there were three papal lines, a third having started at Pisa by an utterly inept attempt to end the schism), and it is utterly unclear what Ferrer's role was; some say he opposed the withdrawal of support, being loyal to Benedict XIII to the end, and others that he reluctantly recommended it, and if the latter, it is unclear the reason. In any case, the Council of Constancy did not end the stubborn Avignon line, which continued for 25 more years, but cleared up most of the confusion, since only the Kingdom of Aragon continued to recognize it, and while there were plenty of people who continued to think that Benedict XIII was the true Pope, virtually nobody thought any of his Avignon successors were. It is, again, unclear what Ferrer's own position was. Most of our sources about most of Ferrer's life are inconsistent with each other, for that matter, so there's a lot we don't know about Ferrer, although there is enough that we have some notion of the shape of his life, and we do have some of his works.
Ferrer was often called the 'Angel of the Apocalypse' or 'Angel of the Last Judgment' because of his extensive preaching journeys (cf. Revelation 14:6-7).