I know that you can't declare twice attacks against the same objective enemy in the same combat phase. That's ok, but..., can you declare two defenders against the attacks of the same enemy (for example, with boromir -ready himselve- when first attack deals a shadow effect that force another more attack from the same attacker)...

Yes.

If the character is ready, there is no limit of times he can be used to defend...

Wait, that is quite unclear and confusing.

two defenders against one attack is not possible.

one defender defending one attack, then readying then defending another attack is possible.

I know that you can't declare twice attacks against the same objective enemy in the same combat phase. That's ok, but..., can you declare two defenders against the attacks of the same enemy (for example, with boromir -ready himselve- when first attack deals a shadow effect that force another more attack from the same attacker)...

If I understand correctly, you're asking that if a single enemy attacks twice (presumably through some card effect), can the same hero defend against each attack.

The answer is yes, provided he meets all the normal requirements for defending (primarily, that you can exhaust him a second time). These are two separate attacks, just as if they were made by two different enemies.

ok thanks, i meant two diferent attacks by the same enemy (when shadow effect triggers a second attack).