House Of Zinc: Pain

Malachite and Kyanite are demon twins of royalty. Their father took over the crown when their mother died. He started a war with the angels. As the war becomes tense, he sends Malachite and Kyanite to Earth in search for two holy ancient stones that can kill any devil. He orders them to search for the stones and destroy the stones. While on Earth Malachite becomes infatuated with a human he seems to be connected to.

Kyanite's side of the story by @jaxzearcher, House of Zinc: Healing