Great story. I did laugh when I found out what happened to Neville--he splinched himself trying to get away from Severus's pet. I like how the two of them fall into a relationship at the end.
Neville as secret-keeper was surprising, but made sense.
The real story-stealer was the legserpent. She was so protective of Severus. She was also hilarious. "He left meats behind...He wasn't using them any more. Wasteful." I laughed out loud at this part.