In 1260 Theodore married Maria Vasilievna (born between 1243 and 1249), the daughter of Prince Basil of Yaroslavl.

[3] Bored with his status, around 1266 Theodore left his family and on his own initiative went to Sarai, the capital of the Golden Horde.

Theodore the Black took part in Mengu-Timur invasion in Ossetia, in 1277–1278 he headed the punitive campaign in the Volga Bulgaria.

With the marriage Theodore received a huge dowry (according to the fasti, 36 towns) and rose to prominence in the Horde.

In 1290 Michael Theodorovich died in Yaroslavl, so Theodore the Black with his Jarlig from the Mongols returned in the city to rule.