What karmic seeds are there in the mind-essence of an arhat's eighth consciousness?

The arhat, abiding in nirvāṇa with remainder (sopadhiśeṣa-nirvāṇa), passes the days in accordance with conditions, without grasping (upādāna) at any dharmas of the five-aggregate world. His mind is empty of self, and the karmic seeds of the dharmas of the three realms gradually disappear. Because there are no longer any karmic seeds of the three realms, there will be no three-realm world in future lives, much less a five-aggregate body born into the three-realm world. If karmic seeds of the three realms still remain in the arhat's eighth consciousness, those seeds must manifest in order to recompense the karmic actions, and then there would be no such state as nirvāṇa without remainder (anupadhiśeṣa-nirvāṇa).

However, after the arhat enters nirvāṇa without remainder, sooner or later he will reappear in the three-realm world, because before entering nirvāṇa the arhat had heard the Mahāyāna teachings and planted the seeds of the Mahāyāna dharma. Once those seeds mature, the eighth consciousness will output the consciousness-seeds of the manas, giving rise to the manas, entering the neutrino-body (antarā-bhava), taking rebirth once again, and cultivating and studying the Mahāyāna.

Karmic seeds correspond to the manas, and the manas corresponds to karmic seeds. If the manas does not grasp at the three-realm world, it cannot retain worldly karmic seeds; if there is grasping, it will continue to create wholesome and unwholesome, true and false, good and bad (kuśala-akuśala, satya-mithyā, śubha-aśubha) karma, karmic seeds will be left behind, and in future lives one will continue to take rebirth and transmigrate in accordance with those karmic seeds. If the manas does not grasp, the six consciousnesses create no karma, there are no karmic seeds, and there is no need to undergo karmic retribution.