Severus fought Frank alongside Aquila, and ended up failing at trying to keep Agnes from being hurt when Regulus thought it would be oh so impressive if he used sectumsempra on her. He also managed to get a couple of rather nasty hexes courtesy of Lupin, and certainly tried to return the favour for Lupin & Pettigrew. He is sore the next day and will probably be sore for the next couple of days, but will be fine by no later than the end of the week.
Kate showed up and got injured slightly by Lucius and Leoben, although she didn't almost die until Dolph showed up and totally kicked her ass. Elle (being an awesome BFF) saved her from the righteous anger of Dolph and took her to Mungo's where she currently is recovering from massive burning on her right side and a nasty sectumsempra. :(