DEATH!!
That's the only thing that came to mind when Mira thought about her black tail. The aura of death that surrounded her tail was so immense that even Mira, the owner of the tail, felt reluctant to use its ability.
Her instincts were telling her not to use its ability so lightly and that it should only be used in times of extreme danger.
Although she didn't know why she felt this way, that didn't matter. She trusted her instincts.
However, that doesn't mean she can't speculate what her black tail would actually do should she activate its ability.
From what she could tell, there must be some connection between her tail and the black runes that appeared all over her mind, body, soul, and Qi.
Well, that's only speculation, but Mira felt like she wasn't too far off from the truth. Now, what she can do with this information is a different story. She has basically no information on the black runes or what they can do.