[Corinthian]

The rate of hero acquirement is based on you luck scales. Or 3% chance of a hero per turn -+1% per luck point. Its not a random event, it is a separate check.

Some nations can get infinite heroes through so called Multi-heroe chassis. Other nations have a limited amount of heroes.

In vanilla some nations have few, or no(?) heroes at all (Patala?). Other nations only have terrible heroes that are little better than indy commanders. (MA Ulm). Lanka is special in that it can actually get units that it can summon as heroes, witch is rather underwhelming.