immortal time time travelers, i.e., the Time Patrol members;
Danellians, who founded the Time Patrol;
In fantasy, it is unnecessary and probably wrong to explain the powers of the gods because any explanation or rationale transforms fantasy into sf. Danellians are the next stage of evolution after humanity. Immortals are ordinary human beings who merely live longer. Time travelers are ordinary human beings with access to time machines - usually, although, in There Will Be Time, they are mutants and I have tried to show that the Time Patrollers surely transcend any ordinary perception of time. Also, on several occasions, they are perceived as gods or angels by people in the past and, to the Patrollers themselves, Danellians are god-like. However, real "gods" are those whose powers are a mythical or fictional premise not requiring any explanation.