Hi again...!

I'm playing the second quest: 'Journey in the dark' whit that good fellow... the Balrog.

for the fist time I place 5 progress token on the Great Bridge and i still have 2 damage tokens on the Doom Doom Doom objective.

in this situation I don't have to discard the hero... or i must discard it to go on and the balrog will never get the damage?

The effect on Great Bridge is a response, which means it is optional. So if the Balrog is not in play you don't have to sacrifice a hero.

it means that if the balrog is in play I have to sacrifice my hero?

or it is optional?

tks!

It is optional.

In campaign, you'll got more burden cards if you don't kill it though.