Pope Francis will elevate 13 Roman Catholic prelates to the high rank of cardinal next month, including 10 “cardinal electors” under 80 years old and thus eligible to vote in an eventual conclave to choose his successor.

The surprise announcement was made at the Pope’s weekly Sunday address, where he said that the ceremony to invest the cardinals will take place on Oct. 5.

Cardinals are among a pope’s closest advisers in Rome and around the world. Because most are eligible to elect a new pontiff after Francis dies or retires, their choice is the most concrete way a pope can put his stamp on the future of the Roman Catholic Church.

The new cardinals come from countries including Spain, Portugal, Indonesia, Cuba, Democratic Republic of Congo, Luxembourg, Guatemala, Italy, Canada, Britain and Lithuania.

One of the appointments, Czech-born Canadian Michael Czerny, is the Vatican’s expert on migration, reflecting Francis’s defense of immigrants.

Three others reflect his concern over relations with Islam.

One is Archbishop Miguel Angel Ayuso Guixot, head of the Vatican’s department for inter-religious dialogue; the other two are archbishops in Morocco and Indonesia, both predominantly Muslim countries.