Kostroma (deity)

Then, participants of the rite mourned the death of Kostroma, and burned or tore the scarecrow.

And then, by the order of the Ruler of the Underworld (probably Veles or Chernobog), Sirin and gusi-lebedi (The Magic Swan Geese) stole Kupalo and carried him into the Nav.

[1][2] Many years later, one day, Kostroma walked the shore of the river Volga and made a wreath.

Kupalo and Kostroma fell in love and shortly were married without any knowledge that they were brother and sister.

Kupalo has jumped into the fire and died, while Kostroma ran to the forest, threw herself into the lake and drowned.

Walking around that lake, she charmed the men she met on her path and dragged them into the water abyss.

One of the versions also describes the suicide of Kostroma and Kupalo differently: the lovers joined hands and threw themselves off the cliff into the river.