Another show, another night of drama—the fifth episode of Gossip Girl’s final season aired last night, and the fashionable Upper East Siders made quite an impression at the annual debutante cotillion. Serena van der Woodsen (Blake Lively) and Blair Waldorf (Leighton Meester) both sparkled big time. Serena stunned in a strapless Monique Lhuillier navy dress with black sequin detailing, while Blair looked chic in a black sequin cap-sleeved number, which she accessorized with Graziela crystal earrings. For more looks from the “Monstrous Ball” episode, click through the gallery. And catch Gossip Girl Mondays at 9/8c on The CW, then come back to news.instyle.com for our weekly fashion credits.