On his unfortune, Citadel forces, alleged allies of Rann, attack Thanagar just as Isamot's mate enters her only receptive mating period. Isamot then must choose between his partner and the only possibility of a family. He chose his partner but by the time he returned she had taken another mate. With the mating urges over he returns to full duty. He later visits Mogo on Vath's advice for Mogo to council him on the pain for his recent loss, but rejects the therapy after noticing something is amiss when Green Man is behaving strangely. When he, Vath, and Bzzd were sent after Guy Gardner, who was accused of murdering two fellow Green Lanterns, and confronted him on Mogo, Isamot was the first to believe Guy's story of something bizarre happening on Mogo due to his earlier suspicions. After arriving later, Soranik Natu, a medical expert, confirms that Mogo is infected with a disease created by the mushroom spores laid across its surface, and Isamot assists his fellow Lanterns in curing Mogo, while fighting off Kilowog, due to Kilowog also having been infected.