Immortals. Twin princesses, Ella and Elle. Black Wings of the Night

The third book in the cycle “Legends of the Russian North. So, the Dead Princess Alma fell asleep, and troubles came to the Siberian lands. Elder Ouma, the proud Savir, wanted to take all power into his own hands. Nothing stopped him along the way, neither vows nor Covenants. A terrible feud took up a forest fire. And who can now stop the terrible war? Only sisters, Ella and Elle.