Sylvester (Russian: Сильвестр, romanized: Silvestr; later known as Spiridon)[1] was a priest of the Cathedral of the Annunciation and a close advisor to Ivan IV.

Sylvester is known for heavily influencing Ivan and the contemporary Russian government alongside Alexei Adashev and their Chosen Council from 1549 to 1560.

[3] The details of Sylvester's early life are largely unknown, as most biographical information on him is from inscriptions in books he donated to religious institutions.

[1] It is known, however, that he operated a workshop in Novgorod with connections to the Cathedral alongside his son, Anfim, where he presumably acquired his skill at copying, trading manuscripts, and icon painting, before moving to Moscow at an unknown time.

[4] In 1553, when Ivan the Terrible fell sick and Prince Vladimir Staritsky tried to visit him, the boyars would not allow it until Sylvester forced them to, gaining further favor with the Tsar and his family.

[1] Sylvester used his power mostly to push for a stricter religious society within Russia, advocating for the accelerated Christianization of Kazan and urging the Tsar to cast his sinful vices away.

[1][4] Sylvester decided they must denounce the two to the Tsar, and Ivan ordered an investigation, which linked Bashkin's friend Artemii and his student Porfirii, as well as many other priests, to the heresy.

[1] Months later in October 1553, a d'iak named Ivan Viskovatyi accused Sylvester of sharing the views of Bashkin and Kosoi.

[4] When this death occurred is not precisely known, but it must have been before 1580, as the Kirillov monastery recorded his and his son's legacy in that year, so they both must have been dead prior.

[1] In the letter, Ivan accuses Sylvester of using the promise of spiritual guidance to manipulate him, therefore supplying himself with his unofficial but nevertheless substantial political power.