He had been thinking about the locket since Christmas.
Not about destroying it — that part was straightforward, he had the fang and the method. The problem was access. The locket was a Horcrux, and Horcruxes were sealed. The diary had not needed opening; the fang had gone through the cover directly. The diadem was unwrapped and struck. But the locket was different — it had a catch, a mechanism, and in the books it had not opened through any ordinary means. It had opened for Harry. In Parseltongue.
He had been carrying this problem since talking with Kreacher, turning it over in the way he turned over problems that did not yet have solutions, filing it and returning to it, filing it and returning to it.
He tried it alone first. During a late evening in his room, the locket — still in Kreacher's keeping, not yet in his hands — present only as a memory of what he had read. He tried to produce the sounds Harry made when he spoke to snakes: the specific sibilance, the distinctions of pitch and duration. His mouth could approximate the shape of the sounds. It would produce the magic in them. He knew this before he tried as canon had confirmed it by the end of the war .
What he needed was a Parselmouth to learn more words.
He thought about this carefully. He thought about how to ask Harry without explaining why, and whether a partial explanation would be sufficient, and what Harry would and would not accept as a reason. Harry was not a person who required complete information before helping someone he trusted. Harry was also not a person who could be managed without noticing the management. The approach needed to be honest within its limits.
He settled on academic interest — which was true, as far as it went. Parseltongue was genuinely the most documented rare magical ability with a living practitioner. He had been meaning to study it for entirely separate reasons. The locket was the reason he was studying it now rather than later, but the interest was real.
This was the kind of truth that was not a lie and was not the whole truth, and he had become, over the year, reasonably good at offering these when the alternative was a conversation he was not ready to have.
He would ask Harry on the train.
He had candidates. He would test later.