Severus chuckled. "She turned up on my doorstep after my first day teaching and as Head of House with Filius Flitwick and Pomona Sprout in tow, all with a bottle of some sort of alcohol in their hands. They rather firmly drew the line between Severus Snape, student, and Severus Snape, fellow sufferer in the world of teaching and being Head of House." He cocked his head slightly. "It was... good. She was... a friend or as much of one as I could allow with what I had to do." Then he snorted and rolled his eyes. "Mind you, she loathed me last time I saw her since she thought I was the Dark Lord's man. Why she was still so convinced of that after I was so soft on her Gryffindors when they broke into my office, I'll never know." Of course he did know. He'd killed Albus. She'd struggled to get past that, unsurprisingly.
"Slughorn knew," he replied. "I'm not sure how much. Albus was cagey about that - I think he thought I was going to get ideas or something - but he did tell me that's how the Dark Lord found out about it, back when he was just Tom Riddle."
"I will never understand why Albus did what he did. Or didn't do things. He never chose to explain much to me. I was just his useful tool." He sneered briefly before shrugging his shoulders as if tossing that away. As always, his feelings for Albus were tumultuous. "What of the other countries?" he asked with an arched eyebrow. "Have they been affected by whatever happened here? And if not, where are they? Which leads me to my next pertinent question - what did happen to cause this?"