after gelasius ii's death, when calixtus ii had been elected pope in 1119, henry v was induced to change papal allegiance, in the concordat of worms of 1122. calixtus ii entered rome, and gregory viii left, going to sutri, where he was in april 1121, when papal troops of calixtus ii closed up the city for eight days until its citizens surrendered antipope gregory viii. he was taken to rome and imprisoned in the septizonium. after having been moved in confinement from monastery to monastery, he finally died at la cava, salerno, some time after august 1137.