Sasha

Sasha is a female vampire. She is only mentioned in Breaking Dawn, and was part of the Denali Coven.

Personal history
Sasha was the creator of Tanya, Kate and Irina. They thought of her as a mother and are still upset about her execution. She was the one that created Vasilii, one of the Immortal children. She kept his existence from Tanya and her sisters, to save them from the fate of being executed by The Volturi, which seems that she knew it was going to happen.

Death
Due to the danger of the Immortal children revealing the existence of vampires, The Volturi got involved and executed Sasha by means of burning, with Vasilii in her arms. Tanya and her sisters witnessed their death.