Kostroma is an East Slavic

East Slavs

The East Slavs are Slavic peoples speaking East Slavic languages. Formerly the main population of the medieval state of Kievan Rus, by the seventeenth century they evolved into the Russian, Ukrainian, and Belarusian peoples.-Sources:...

 fertility goddess. The rites of Semik

Semik

Semik is an ancient Slavic fertility festival celebrated in early June and closely linked with the cult of the dead and the spring agricultural rites. It usually fell upon the Thursday of the Green Week...

 were devoted to her. During this festival a disguised girl or a straw figure portrayed Kostroma. First, a scarecrow

Scarecrow

A scarecrow is, essentially, a decoy, though traditionally, a human figure dressed in old clothes and placed in fields by farmers to discourage birds such as crows or sparrows from disturbing and feeding on recently cast seed and growing crops.-History:In Kojiki, the oldest surviving book in Japan...

 was honored and revered. Then, participants of the rite mourned the death of Kostroma, and burned or tore the scarecrow. Rituals with Kostroma were aimed at improving soil fertility.

The scarecrow of Kostroma is part of East Slavic folklore

Slavic mythology

Slavic mythology is the mythological aspect of the polytheistic religion that was practised by the Slavs before Christianisation.The religion possesses many common traits with other religions descended from the Proto-Indo-European religion....

.