Mira sat in the middle of a massive empty sphere. She was obviously still underground, but her black tail's ability obliterated everything within a few hundred-meter radius. However, this also confused Mira slightly.
Her instincts told her that her black tail's ability was DEATH, but she wasn't sure exactly what that entailed. She thought it could only be used against living beings, but looking at the destruction around her, it seems her tail doesn't differentiate between animate and inanimate objects.
Or maybe, this is just an aftereffect of using such a deadly ability.
Though, it technically wouldn't be wrong to say she didn't 'kill' the stone and minerals around her as they no longer exist.
Mira shook these thoughts out of her mind and focused on her surroundings. Although it was dark in this cavern, she could still see relatively well. So, she was able to make out many small tunnels stemming from the cavern she accidentally created.