Quindecimviri sacris faciundis
In ancient Rome, the quindecimviri sacris faciundis were the fifteen (quindecim) members of a college (collegium) with priestly duties. Most notably they guarded the Sibylline Books, scriptures which they consulted and interpreted at the request of the Senate. This collegium also oversaw the worship of any foreign gods which were introduced to Rome.
Originally these duties had been performed by duumviri (or duoviri), two men of patrician status. Their number was increased to ten by the Licinian-Sextian Law in 367 BC, which also required for half of the priests to be plebs. During the Middle Republic, members of the college were admitted through co-option.