Remus/Neville
I think that it'd be easier to answer what didn't happen my last year. The year before, at the end, Dumbledore was killed by Death Eaters, and then that summer You-Know-Who took over the Ministry. Snape was named Headmaster, and the Carrow twins were hired to teach the Dark Arts and Muggle Studies. Both classes were required for every student.
[...]They taught [...]
They did away with Defence Against the Dark Arts, and we were taught Dark Arts, instead. [...] They made all of us, each one of us, learn to do the Unforgiveable Curses. Except for the Killing Curse, [...] we all had to practice on each other, or we would be put into detention.
It was utter hell, and then there was the final Battle, and I saw a lot of good people killed, and a lot of bravery. I never want to see anything like it again.