Remus frowned at the mention of Peter. He'd managed to avoid seeing his former friend easily enough -- Peter avoided all contact with the rest of the staff. And, Remus wasn't about to go looking for him. He'd left the door open. That didn't mean he was going to walk the proverbial widow's walk looking for Peter to come to him.
Even Remus had limits.
"In that case," he smiled again, putting thoughts of Peter far from his mind for his own sanity, "I'm glad I merit a warmer welcome and shall be wary of whatever payment is exacted for my trespassing."
Slipping a folded bit of parchment from the pocket of his robes, he glanced around for the nearest available flat surface and motioned silently for permission to use it. "If it were any Headmaster but the current one, I'd say you're not likely to get in trouble at all. But, given who the current Headmaster is...well, he at least likes you!" Remus laughed, thinking Severus was probably going to throw a conniption fit if he found out Remus had dared bring this particular item into the castle, no matter how benign the intent.
Spreading the parchment out to it's full expanse, he pressed his thumb to one of three faint reddish spots in the bottom right corner and murmured the old passphrase, I solemnly swear I am up to no good. Instantly the previously clear parchment shimmered, what appeared to be dark ink spreading rapidly over it until the whole was covered in what resembled ancient blueprints, but was in reality a complete -- or as complete as four teenaged boys with a penchant for sneaking around could make -- diagram of the castle in which they currently resided. All levels were represented, all towers. Anything they could have seen themselves or sussed out with charms, everything Peter had scouted in his rat form, it was all there.
And moving around the surface were tiny dots in blue, green, and black with labels giving the precise name of the person represented by each dot. That had been their crowning achievement with this map. It never lied. The labels were always one hundred percent accurate about the identity of a person, no matter what shape or guise they wore, visible to the naked eye or not.
"Regulus, what you are looking at is the Marauder's Map," he said, looking up with a proud grin.