He has always known that a child of Mikhail will be his lifemate, so when Raven, Mikhail's lifemate, is attacked, he gives her his blood to build a bond between them.
Given their predestined relationship, he had always assumed that a child of Mikhail would be his ideal companion, and when Raven, Mikhail's ideal companion, was targeted, he sacrificed his own blood to form a strong connection with her.