Envy had been spending so much time on his "Virtue project" that he ignored everyone else. He was consumed with how far he could go. Eventually, Temperance could only hold on but so much. Her breathing was incredibly shallow, the room closing in on her. Envy had tested and pushed her beyond boundaries that any human body could take, but she was strong---so she'd held on as long as she could.
He was changing her dress, fitting it over her head when Sloth slinked in. Temperance looked ashy, gaunt, she wasn't the plump, confident Virtue. The look in her eyes looked lifeless. She didn't have the fight in her anymore. Envy was excited of photographing her dead body, because then he had a record of his experiment.