what happen when the overlord attack with the blast a target without dodge and another character is adjacent andis dodging? can he dodge the attack? and what happen if the target space is without any character? can the adjacent character in the blasted area dodge(if they are in dodge order?)

If dice are rerolled due to any of the figures in the blast attack's radius dodging, they are rerolled once and the result after the reroll is applied to all involved figures. This does mean that a figure can protect another by means of dodging. It does not matter whether the dodging figure was initially targeted or not by the blast, being within the blast radius is enough.

So in both your examples, the Overlord rolls dice, the dodging player decides which ones he has to reroll, the Overlord rerolls, and then all the figures within the blast radius take damage according to the rerolled dice.

I too found this to be a bit counter-intuitive at first, and we house ruled it (back in Doom, actually, which I had before Descent) to only figures actually dodging being affected by the reroll. It's one of the many instances where Descent sacrifices logic to simplicity though, and it's perfectly playable by the rules - we're no longer house ruling it meanwhile.

haslo said:

i knew but my current overlord does

not believe

Its in the GLoAQ, which is official responses:

Area of Effect attack and Dodge.
An area attack is made on a group of characters. The attack die are rolled and one Hero uses Dodge. Does the original roll take effect on the other Heroes, or does the newly rolled attack affect all Heroes?

The new roll effects all the targets.