Severus spins around with his wand out and aimed before the rest of his body is even halfway turned. He gives Gaav a measuring, deeply wary look. "Good afternoon. I don't believe I've had the pleasure." The look re-measures. "And I do believe I would have remembered."
No immediately evident glamours, the bones are, however rough-hewn, still too fine for giant or troll heritage, the body spilling out magic (Dark magic, too) like a Draco as an infant having a temper tantrum over peas--no, like Potter having a temper tantrum over Snape still being alive, since there aren't any immediately obvious effects of the roiling presence--bloody enormous sword (those can serve almost as well as wands for focusing magic, can't they, unless they're pure iron?), raincoat more eye-blinding than Albus, Lockhart, and Slughorn standing side by side.... too tall for one of his former associates, at least...