Complex sentence: An accomplished or realized practitioner (by maintaining conscious awareness during the death process) can choose to return to samsara, that many lamas choose to be born again and again as humans and are called "tulkus" or incarnate lamas.
Split into simpler sentences: An accomplished or realized practitioner (by maintaining conscious awareness during the death process) can choose to return to samsara. They believe many lamas choose to be born again and again as humans and are called "tulkus" or incarnate lamas.