The Seven-Stringed Zither by Baisha
Synopsis:
Luckily, she was clever enough to plant a drop of her own heart's blood in the heart of her most beloved disciple while he was still at her side. Otherwise, that traitor would have killed her long ago. But when she woke up, she caught her disciple in bed with the fox immortal who had been pestering her for nine thousand years. That would have been bad enough, but what on earth was that position? Everything had gone wrong. She was a dignified ancient deity, and losing her true form to a little immortal was one thing, but why did she also have to put up with that shameless fox's insults? In a fit of anger, she sealed herself away in the Land of Nine Coldness. But why did the Heavenly Emperor, her dear brother, have to cause her more trouble?
He was merely one tiny spirit bird among the many bird and flower spirits in her immortal palace. Perhaps he was not even a spirit bird, since he differed from all the others: his entire body was snow-white, without any bright colors, and he had no gender. Still, he clung to his love for her. He never expected that love to be used against him. With no other choice, he decided they would perish together, carrying his feelings for her with him into the underworld.
Boys, it feels pretty good. Now that it's set, don't change it. By the way, will there be any training?