Discussion of the Necropolis faction.

Regarding the Mage, I can offer this advice: in the campaign, it's better to choose a Blood hero, as the first level of Blood provides an excellent buff to the power of attacking spells. In a duel, however, it's better to choose a Tears hero. I haven't tried the Necropolis Warrior.

If you take the first level of reputation, you can change it by taking the second level of a different reputation. If you have developed a hero's reputation to the second level, it can no longer be changed. By the way, the achievements "Repentance" and "Rewind" hint at this :).