"Are - you - mental?" -- Ron Weasley
Hermione Apparates with Harry to the Forest of Dean, where Harry, keeping watch late at night, sees and follows a Patronus in the form of a silver doe to a frozen pool in which the sword of Gryffindor lies. He is nearly strangled by the locket Horcrux’s chain when he dives to retrieve it, and is saved from drowning by Ron, who has been shown the way back by the Deluminator. Ron then confronts and destroys the Horcrux after Harry commands it to open in Parseltongue. They return together to camp, where Harry has to protect Ron from Hermione.
Calendar and Dates
Begins at midnight, so it is the day after the preceding chapter, Boxing Day (26 December), 1997.
Interesting facts and notes
'The Forest of Dean,' she said. 'I came camping here once, with my mum and dad.'
JKR lived in a village at the edge of the Forest of Dean for several years.
After two nights of little sleep
Those would be the nights of the 24th and 25th.
He remembered the sound of a cloak slithering over dead leaves many years ago
About five and a half years ago, in the spring of his first year when he visited the Forbidden Forest for the first time in search of a wounded unicorn (PS15).
'I'm going to ask it to open, using Parseltongue,' said Harry.
This reminds me of a scene in The Fellowship of the Ring, from book II, chapter 4 "A Journey in the Dark": the fellowship facing the gates of Moria, when Gandalf suddenly realized that all they had to do to open the gates was to ask them to open in the language of the elves who had once been Moria's closest neighbours.
Here, though, the situation is neatly inverted - Voldemort made the command the simplest possible, true, but in a language that he thought he alone could speak.
Behind both of the glass windows within blinked a living eye, dark and handsome as Tom Riddle's eyes had been before he turned them scarlet and slit-pupiled.
Or did they only change to that appearance after he created this Horcrux, I wonder?
'My name. "Ron."'
So in addition to the Death Eaters (see DH20), Dumbledore, the creator of the Deluminator, could key spell effects to be triggered when the target person says a keyword, or at least a specified name.
Exceptional character moments
Ron's confrontation with the Horcrux, and Harry's remarks afterward.
Hermione tearing into Ron, which I personally quite enjoyed watching.
"Where 'chivalry' entered into this, he thought ruefully, he was not entirely sure, unless it counted as chivalrous that he was not calling for Hermione to do it in his stead."
"'Stuff like that always sounds cooler than it really was,' said Harry. 'I've been trying to tell you that for years.'"
"Her voice was now so shrill only bats would be able to hear it soon"
"arms and legs crossed so tightly it seemed unlikely that she would unravel them for several years."
"Could've been worse. Remember those birds she set on me?"
"I still haven't ruled it out."