From the analysis of sources on the topic, the following conclusions can be drawn:
1, the only authoritative source that reports the "Kyiv prince" Theodor, is the "Tale of Vasily Kalika," written shortly after the events themselves, roughly in the 1330s. Despite the fact that it came to us in relatively late copies, its authenticity is beyond doubt.
2, "Beneshevich’s Excerpts", mentioning some Theodor, do not call him a prince and do not associate with Kyiv. This is another person who has nothing to do with Theodor from the "Tale of Vasily Kalika". The time and circumstances of the origin of the "Excerpts" have not been clarified, this issue requires further study.
3, the mention of the Gustynja Chronicle under the 1361 – 1362 years about the "prince Theodor" is the result of an unsuccessful combination of the author GL, made on the basis of the "Tale of Vasily Kalika" (through the Nikon chronicle), the "Tale of Podillja Land" (through a "Lithuanian" chronicle, presumably Lit5L) and "Descriptions of European Sarmatia" by A. Gwagnini. They have no independent source value, but only show (along with other combinations of the author of the annals) the level of the Kyiv historiography of the early 17th century.
I call Feodor ephemeral prince, because we are only talking about him, but we do not know when or how he became a "prince", nor his other deeds, nor his end. From the fact that the news of 1331 was the only one, one might think that his "reign" was not long and the territory of his "power" was not extensive. With a detachment of 50 people, even in the 14th century. you will not get much.
Of course, Theodor was neither the first nor the last among such self-proclaimed princes atamans on our lands. We have enough of them, even more than the "real" dynastic princes. I plan to trace several stories of such a rise "from the dirt and into the princes", but this is the topic of the following articles.