Threats of torture but if you REALLY think Krait would harm a dumb creature like a slug after following her fortunes this far you don't know her very well. Rather a short one
Chapter 2: Slugging around with Horace
The village of Budleigh Babberton was as infested with mist as everywhere else seemed to be since the dementors had left Azkaban. Krait and Severus arrived quietly with Sirri and Beloc to help deaden their arrival from any listening wizard and proceeded to the house where Dumbledore had said Horace Slughorn was staying. It was a small, neat stone house in its own garden; and Severus and Krait walked serenely up the path in the wake of the postman.
"They're on holiday, mate" said the postman cheerily. "In the Canary Islands. Still get junk mail and bills o'course"
"As inevitable as death and taxes" said Severus. "I was told they have a house sitter though, who would doubtless be glad to have that dangerous gas leak seen to before he gets blown up in his bed…"
"Let's hope you're right, mate!" said the cheerful postman, whistling his way back down the path.
Severus knocked.
There was no answer.
"Well, if he was listening he didn't take my bait about the danger…he may have recognised me" Severus murmured. "alohamora"
the door yielded under the spell; and they entered a small neat room with good quality furnishings and a rather overstuffed armchair that made the place looked cluttered. Krait's eyes narrowed and she dug her wand hard into the chair.
"We can do this the easy way, Professor Slughorn or I can force you back into shape" she said. "I can, you know….though I'm intrigued by a non animate shapechange, I'd not have thought of it… to retain the awareness thus…."
The chair yelped when she prodded it and warped back into the shape of a fat, bald old man with a huge silver walrus moustache, massaging his belly.
"Who are you? Dumbledore I half expected…. Snape" he said, seeing Severus. His tone was not totally warm.
"Slughorn….we shan't take much of your time."
"Unfair to creep up on a fellow hiding behind legitimate muggle callers…."
"And failing to give you a chance to set a better scene? Krait here is impressed by your ability with Transfiguration, it's a speciality of hers too, she's an animagus."
Slughorn regarded Krait with more interest.
"You are, are you? What form?"
"Snake" said Krait. "For a Slytherin quite appropriate, don't you think?"
"Indeed, indeed…." He rubbed his hands. "Used to be head of Slytherin myself, once….Snape is now, I believe?"
Severus gave a frosty bow.
"I have that honour" he said. "But whilst we are here to reminisce it is not about the excellencies of House Slytherin….more about one of its deficiencies…"
"Indeed?"
"Why don't I fix coffee?" said Krait. "Then we can talk…."
"I'm not coming back to Hogwarts" said Slughorn.
"No need….if you cooperate" said Krait, coldly. "I want to talk to you about my father."
"Your father? I don't think I know….Lucius Malfoy?"
"No. Tom Marvolo Riddle" said Krait coldly and precisely.
Slughorn paled.
"Really, I'm sure there's nothing…"
"Harry is my friend" said Krait. "He has to fight my loathsome father to the death, the man who killed his parents, including your favourite, Lily Evans….there is nothing I would not do to help protect my friends."
Horace Slughorn smiled. It was a little forced.
"Rather melodramatic, young lady."
"I get that from my father" Krait let her eyes fill red and Slughorn jerked involuntarily away. "Severus says you are too good a wizard to get caught without antidote to veritaserum; or to be legilimensed. But one can overdose with veritaserum….or use the crude but sometimes effective muggle methods of chopping off the odd digit at a time until the torturee cracks and talks. I care what happens to Harry and my friends. I never met you before, so I would care why?"
Slughorn stared in horror.
"Snape, she's a monster!" he said.
"She states her case quite plainly, however" said Severus. "I loved Lily Evans desperately, if secretly….I care more for protecting her son than I do for a teacher who was generally more concerned with the well connected than the talented…it was Lily's charm that drew you to her, as much as her ability with potions; her charm of manner was genuine, unlike Tom Riddle's. I am not squeamish; and Krait has had a horrific upbringing where the sufferings of children were the sport of her supposed guardians."
"You were raised by Death Eaters?" He was horrified.
"No, by sadistic muggles" Krait shrugged. "though I can take the cruciatus curse without screaming….I pass out first, I'm stubborn that way. Are you?" she asked clinically.
"You – you can't use an Unforgiveable curse on me…the ministry…"
"Who needs to? There is an open fire….pokers….electricity burns too and negates any magical defence…." Krait glanced around the room.
"You sound like a Death Eater."
"No, I think not….they enjoy what they do because HE has warped them….I do what is needful efficiently and dispassionately. Would you like to strip, or shall I burn your clothes on you?" she picked up a table lamp and took off the shade and removed the bulb.
"What did you want to know?" he asked nervously.
"It's quite simple….I know you explained to my father what horcruces are, I only want to know if he mentioned any number to you."
Slughorn eyed her with dislike.
"If he had said anything, I believe he was keen on arithmantic significance…." He said. "He might have mentioned that seven parts of anything would be more efficient….."
"He speaks sooth" said Severus "He slipped up on the occlumency…..I saw the boy Riddle ask the question….."
"Good" said Krait. "Then we know what to prepare for…."
"Are you going to kill me?" Slughorn asked fearfully.
Severus looked at Krait and they both laughed.
"Whatever for?" said Krait.
"I might report you to the ministry….."
"For using no magic? For making threats which I had no intention of carrying out? For forcing a box of crystallised pineapple on you as a thank you gift?" she produced a box of the same "Which does not contain veritaserum…..THIS one contains veritaserum" she showed him an identical box with a small mark at one corner. "I hoped you'd tell us for affection for Lily….."
"Well upon my soul….!" Slughorn was indignant.
"Do you think Dumbledore would permit anyone to hurt you?" asked Severus. "Drastic times call for drastic bluffs….though it was all I could do not to laugh to hear Krait using terrible threats when she is the girl who had long arguments with Minerva over whether it was ethical or if it were cruel to turn hedgehogs into pincushions or beetles into buttons."
"She did, did she?" Slughorn looked at Krait anew. The girl shrugged.
"I'm notoriously soft hearted about hurting animals…..though I can stretch a point to hurt Gryffindors occasionally…." She grinned.
"What house is Harry Potter in?" Slughorn asked almost greedily.
"He's a Gryff…..but nobody's perfect" said Krait.
"Like his mother….one should not be surprised…."
"Yes…..she gave her life for him, it was that that created the blood magic that bounced the killing curse" said Krait.
"If you'd told me that I might have spoken to you more willingly!" said Slughorn angrily. Krait fixed him with her intense, violet gaze.
"Would you? I don't think so, sir….you are running scared, you would not I think have given any information that compromised your own safety….only by threatening that could I get through to you….it seemed less unfair than surreptitiously poisoning you with veritaserum in sweeties…."
Slughorn stared, then he gave an unwilling crack of laughter.
"Merlin's beard, you have a strange sense of ethics….but I would never have forgiven a trick like that, never…."
"Then the decision was right….betrayal of trust is dirty, even when it is the only way" said Krait. "If you run scared of Death Eaters, why not come to Hogwarts, not to teach or put a strain on yourself, but under Professor Dumbledore's protection in a secluded wing in comfort?"
"With all that has happened there? A death Eater on the staff only last year? I couldn't!"
Krait shrugged.
"Well, if you change your mind, I think it's the safest place in the world; and I'm sure Professor Dumbledore would offer you hospitality. I hope you enjoy the unadulterated pineapple….I'll not be offended to know that you'll use the Revelaspell on it" she grinned.
-/-
"You were quite frightening in there" said Severus as they walked away. "You almost had me believing that you were going to do it…"
"I remember despising the nuns when they were hurting us" said Krait "Because they so obviously enjoyed it….to despise them was a victory, it worked against the fear. It struck me that to be utterly emotionless about it would be more menacing, there would be nothing human to hate, despise or taunt."
"I'd say it worked very well" said Severus.