Oberyn stabbed Gregor several times with his spear during their fight, but the injuries have surpassed being mere flesh wounds. It turns out that Oberyn coated his spear tip with manticore venom, which has caused a giant wound on his right side to fester. Grand Maester Pycelle think theres nothing to be done for Gregor, but Qyburn believes there is. Pycelle mocks his attempts and reminds Cersei that Qyburn isnt a maester because he was expelled from the Citadel for his unnatural curiosities. Cersei dismisses Pycelle and gives his laboratory to Qyburn. She asks whether Gregor can truly be saved. Qyburn says its difficult to say, but if his past work is any indication, theres a good chance. He does, however, say that Gregor will be changed, although he most certainly will not be weakened. It looks like Oberyn was a martyr for his cause. Despite being brutally murdered due to his overconfidence, he made sure that Gregor would suffer no matter what. Through normal procedures, Gregor would die, and considering the crimes hes committed, a lot of people would prefer this fate. However, though we havent seen much of his work, we know that Qyburns work involves a lot of...unorthodox methods. Whatever he has planned for Gregor cant be good, although Cersei will certainly be glad to have her favourite killer back in working order.