He is most famous for reforming the office in 1359, increasing the number of posadniks and creating a ruling collective in the city.
In the morning, Ontsifor sent Vasilii across the river to negotiate with Ondreshko and Fedor but did not wait for his return before he and the veche in front of the cathedral took up arms and crossed the bridge to attack the veche on the Market Side, seizing two men (but not Ondreshko and Fedor) and confining them in a church (the chronicle does not say which one - it could have been the cathedral or one of the churches on the market) before Ontsifor broke down and fled the city.
[5] Ontsifor appears to have not stayed away from the city long and reappears in the chronicle again in 1348 leading Novgorodian troops (he was one of several commanders mentioned) against the Swedish king Magnus Eriksson, who was at that time crusading against the Finnic Izhera people living along the Neva River and threatening the fortress of Orekhov.
Ontsifor and the other companions managed to retake the region and kill 500 of the enemy, losing only 3 themselves before returning to Novgorod.
[12] Ontsifor's residence in the Nerev End (borough) was discovered during archaeological digs in the city and was excavated between 1951 and 1962.