Morozova's Stag is an ancient, magical, and magnificent white stag that appears only at twilight. In children's stories the stag can talk and will grant wishes for its captor. Even though this is a child's story and therefore fiction, the stag is an extremely powerful creature nonetheless. According to Baghra, they're illusive and part of the oldest science; the making of the heart of the world.
The stag is first seen when Mal and Alina kiss in Tsibeya. The Darkling's hunters track it down in order to obtain the antlers and make an amplifier for Alina. The amplifier would be the most powerful one ever known.
It appears in The Istorii Sankt'ya