Leadership of the Thebaid Monasteries
Pachomius appointed Theodore overseer of the monastery at Tabennisi and, in time, placed him at the head of the wider network of Thebaid communities. According to Wikipedia he had earlier been made steward of Tabennese and, by one account, demoted for a lapse in discipline, afterward serving for several years as Pachomius's personal assistant and earning the title 'brothers' comforter.'
When Pachomius died in 348 he designated Petronius as his successor rather than Theodore. After Petronius's death and a period of instability under Horsiesios, Theodore became the de facto leader of the Koinonia, administering the federation from Phbow for roughly eighteen years until his own death.
He was the first in his monastery to be ordained to the priesthood, a circumstance traditionally linked to his epithet 'the Sanctified.' He was also well known to Saint Athanasius, Patriarch of Alexandria.