Merkourios 3 was magister militum, at Rome; after the election of Benedict III (Benediktos 7) as bishop of Rome in 855, Merkourios 3 and the bishop of Anagnia, Nikolaos 49, were sent to deliver the decree of the clergy and leaders of Rome announcing the decision to the Frankish emperors Lothar I and Louis II (Lotharios 1 and Lodoïchos 1); en route at Iguvium they were persuaded by Arsenius (Arsenios 3), the bishop of Horta, to give their support instead to the rival claimant to the see, Anastasius (Anastasios 25); they delivered the decree to Louis (Lodoïchos 1) and then returned to Rome, planning to promote the cause of Anastasios 25: Lib. Pont. 106. 6-7 ("Mercurius atque magister militum"). When Lodoïchos 1's envoys Adalbert 2 and Bernard 3 reached Horta and were also persuaded by Arsenios 3 to support Anastasios 25, Merkourios 3 and Nikolaos 49, with two other magistri militum, Christophoros 30 and Gregorios 93, left Rome for Horta to meet the imperial envoys and to add their support to Anastasios 25: Lib. Pont. 106. 9 ("Mercurius magister militum").

(Publishable link for this person: )