Opening the door to the Night Sanctum was easy enough. They don't directly teach you about arcane trickery at the Cromwell Institute, but the forbidden library section is never guarded... and why have a forbidden section, if not to allow curious students to make it the focus of their evening elective?
I'm surprised not to have found Ancient weaponry here, but our adversary is slick. If my studies have taught me anything, their weapon must be hidden behind a different night door.
They're gambling on wasting our time with riddles until we expire, drawing out the conflict... But I'd wager they didn't expect a graduate with a penchant for cracking codes.
So bet it all on red.