One of the monks whom Devadatta incited to join him in stirring up discord among the Sangha, the others being Kokālika, Khandadevīputta and Samuddadatta (Vin.ii.196; iii.171).
Katamorakatissa was held in high esteem by Thullanandā, for we are told that one day, on arriving at a house where she was a constant visitor, and on being told that several of the Buddha's eminent disciples, such as Sāriputta, Moggallāna, Mahā Kaccāna, had also been invited, as they happened to be at Veluvana near by, she expressed great disappointment that these had been invited, when such most eminent disciples (mahānāgā) as Devadatta, Katamorakatissa, etc., were available. Vin.iv.66.
On another occasion, wishing to ordain a nun who was going through a probationary course, she summoned the monks, but seeing a great quantity of food and wishing to let only her favourites enjoy it, she dismissed the monks on a false pretext, keeping with her only Devadatta, Katamorakatissa and their colleagues (Vin.iv.335).
Katamorakatissaka was one of the monks about whom dissatisfaction was expressed to the Buddha, by the two Pacceka-brahma, Subrahmā and Suddhāvāsa. S.i.148.