A Honkai Impact 3rd and Benghuai Xueyuan character. The second Herrscher after Welt Joyce, and dominated the power of the void. She became a Herrscher and started the Second Impact in 2000 at a Schicksal laboratory and has pulled the whole North Siberia into her void realm. Rumours say that she was inhumanely experimented on and tortured by the tests and therefore awakened the Herrscher consciousness inside of her and took the girl's mind.
Sirin perished together with S-rank Valkyrja Cecilia Schariac and four other A-rank Valkyries (Squad Snow Wolf) in a series of nuclear explosions caused by a rain of missiles from Schicksal.
After Sirin's death, her Herrscher core has been divided into four parts, they are called the Domination of Thunder, the Crave of Storm, the Silence of Death and the Contamination of Flame. The four different parts are kept separately by Schicksal and Anti-Entropy.
In the current game era (Honkai Impact 3rd) Otto Apocalypse has created K-423 using Sirin's DNA and techniques that cloned Theresa Apocalypse, his adopted granddaughter. However, this makes Sirin alive within K-423 and possesses a considerable amount of power, which is just as Otto secretly planned. Sirin's power doesn't normally show up, but in some special conditions, her power would burst dealing a large scale of destruction. The mysterious sound in Kiana's (K-423) head is actually Sirin's, but she doesn't have a clue.
Herrscher of the Void however is not the immediate reincarnation of Sirin herself but rather an entirely different entity that is a mixture of them both due to the weapons she possess known as Keys of the Void which this vessel exerted a strong influence upon the powers of the Herrscher and altered her physical form as well.
She is named after the Russian mythological creature of the same name which is usually depicted as a beautiful half-woman, half-bird.
In version 5.0, an ELF form of her was released. In version 6.9, she became playable with the Miracle Magical Girl Mecha/Fire battlesuit.