[DUEL TOURNAMENT IN HEROES V] Life in the Twilight

Question about the elimination mechanic: is it mandatory to eliminate 3 evil and 3 good heroes, or can you do it however you want?

It is mandatory. Otherwise, you might eliminate 6 good heroes from your opponent and take an evil one, which would drastically reduce their selection options and create a significant imbalance. In my opinion, the number of heroes to be eliminated is usually equal for both sides...