Theodoric was an antipope in 1100 and 1101, in the schism that began with Wibert of Ravenna in 1080, in opposition to the excesses of Pope Gregory VII and in support of the Emperor Henry IV.
The earliest record of Theodoric is his signature on a document of the antipope Clement III (Wibert) dated 4 November 1084, where he signs as cardinal deacon of S. Maria in Via Lata.
[1] In a letter of 29 July 1099, Clement III refers to Theoderic as one of those cardinals who anathematized Gregory VII (who died on 25 May 1085) as a heretic and simoniac.
[8] According to the "Annales Romani", the followers of Clement met secretly in Rome, at night, in St. Peter's Basilica, where they elected and enthroned Cardinal Theodoric, the Bishop of Albano, who may have assumed the name Sylvester III.
He was convicted by judgment of the fathers, [10] and immediately sent to the monastery of Santissima Trinità di Cava, near Salerno, where he was compelled to become a monk,[11] or, according to the "Life of Pope Paschal II," a hermit.