AN: This story is going to be 3 or 4 parts.
The first time the Dark Lord orders her to use her body to gain information is shortly after she's finished her seventh year at Hogwarts. She had been a Death Eater for a year at that point and knew she had no choice, but to obey even if she didn't want to do it.
Once you were marked there was no where to run or hide from the Dark Lord there is only obeying and hoping you've done a good enough job to avoid pair or death.
She got the information he wanted and it both pleased and sickened her.
The Dark Lord told her she was special and different from the rest who followed him, the naivety of youth made her believe his words.
The next time he demands she do it again is nearly a year later a week after Andromeda has left home and moved in with a Mudblood.
This time there are no sweet words of being special there is only the not so subtle threat towards her sister if she Bellatrix doesn't obey.
Bellatrix knew then even she wanted to attempt to defect, run and her hide her sister's actions had made that impossible.
That night as the young, naive Auror told her everything she feels a part of her soul dying and belief the cause is fading fast.
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By the time Bellatrix is twenty-one she has risen through the ranks to become the person the Dark Lord trusts the most.
She has killed more people than she wants to remember and has bedded so many it makes her feel sick.
If it's fear of the Dark Lord or fear of what she has become that has made her stay she no longer knows. Some nights she stands outside Andromdea's house and watches her sister untainted by the darkness of her world. Narcissa isn't as lucky as Andromeda she is unfortunately slap bang in the middle and Bellatrix doesn't know if she can keep her untainted from herself or Lucius.
The Dark Lord's moods change constantly about her. One day she is his best and special, the next worthless and unworthy.
She's not sure which one is true or which she wants to be true.
She's lost and scared in a world where there is only death and destruction tainting everything.
If there is a chance for redemption, she doesn't know where to find it or if it will find her.
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A month after her twenty second birthday the Dark Lord orders her to seduce Alastor Moody. He's the best and most untrusting Auror there is, it shocks how short of time it takes for him to bed her.
How after he asks "So what exactly did Voldemort want you to ask me?"
For the first time since she began gathering information she isn't sure what to say or ask whether to kill him or not.
He willingly gives her little bits of information before leaving her in bed and telling her "We must do this again Bellatrix".
She doesn't tell the Dark Lord that Alastor gave her the information without her manipulating him, if the Dark Lord used Legilimency to see if she's telling him everything or not he doesn't say.
He tells her "Well done and next time get more out him".
She's not sure who she feels more used by the Dark Lord or Alastor, who she hates more them or her.