In his Commentaria in Ecclesiasticuм
Blessed Rabanus Maurus Magnentius, Archbishop of Mainz and one of the most prominent teachers of the Carolingian age, called Praeceptor Germaniae
, author of the hymn Veni Creator Spiritus
, says that the false friends who "take thy seat" in Sirach 12:12 are to be understood as heretics, whose doctrine is full of errors and wickedness, crawling like a cancer (sideways). (mlat.uzh.ch (Patrologia Latina), Rabanus Maurus
The last Antichrist, "not the prince himself alone, but his whole body, that is, the mass of men who adhere to him, along with him their prince" may sit "as the temple of God", "as the Church of God as if he were the Church of God." (St. Augustine on 2 Thess 2, cf. Reply #106, Reply #188)
The Antichrist and his body, "sitting in the temple", are also the "abomination of desolation standing in the holy place" (Mt 24:15), occupying seats in the Church, such "that the word of truth has stood, as it were, when it was not the word of truth, but the desolating abomination" (Opus Imperfectum in Matthaeum, homily XLIX, prophetic perfect tense
), taking the seats of the successors of the apostles.
The Vatican Council says that there will be a Pope and bishops "usque ad consummationem saeculi". It seems obvious what is to be expected during the consummation, during the tribulation, during the reign of Antichrist and his minions.