"Open the door." Arad said calmly, and the demon woman slowly turned around and opened the door with her shaking hands. There was something strange about Arad's voice that she sensed, a deep darkness boiling from within…and she immediately noticed the source. An ancient curse by Doma.
The curse Doma cast upon Arad's voice was a powerful one, any weak demon that didn't follow his order would get slowly weaker and eventually die. Depending on their power, the curse could take any time from minutes to weeks or years to finish them off.
"You're one interesting demon, aren't you?" Doma noticed that the demon had picked up on her curse. Not many could do that, probably since she was constantly experimented on by Sawless that she became that keen on noticing strange magical effects.
The black rain...hoho...the demons don't know.