situation:

Old Bear Mormont stands on 6 +1 (the wall)

He gets -1 from Unsullied, - 4 from dracarys and then gets Plazaed of Punishment for -2 and dies (it is not the end of challenge phase yet)

1.He is saved by the dupe

2. the dupe is lost and at the end of the challenges phase Old Bear lands in a dead pile

Straight from p19 of the Rules reference:

x x If a constant ability or lasting effect imposes a

condition upon a card that would continually drive

it from play (for example, a lasting effect that applies to

a character over a period of time, and kills that character

if its STR is 0), any attempt to save the card must

also remedy the ongoing condition. Otherwise, upon

resolution of the save attempt, the card is immediately

re-exposed to the ongoing condition, and removed

from play. Therefore, if the save effect does not also

remedy the ongoing condition, it cannot be initiated,

as the effect has no potential to change the game

state. As such, using a duplicate to save from such an

ongoing condition is also prohibited.

What that means? As soon as he hits that 0STR condition of Plaza of Punishment's terminal burn, he dies - and since a duplicate wouldn't actually save him, you can't even try to use it. You'd need a risen-from-the-sea like effect (but that only works on GJ characters) to both save AND remove him from what used to be called the "Terminal" state.

Sorry, but this is a newby question.

What is dupe?

Duplicate. You can attach extra copies of unique characters to serve as "extra lives."

Think about this as the following:

He is at 0 str, right? As long as he is at 0 str until the end of phase he will die.
Even if you use DUPE, the second (or milisecond) right after, he is still at 0 str, which makes him die again.

I don't know if the dupe should go to discard and the char to dead pile (seems the most logical), but the dupe can't save the char for sure, as long as somehow it's not the end of phase.

If a card with a duplicate leaves play for any reason, the duplicate goes to the discard pile. (See "Leaves Play" on p. 12 of the RRG.)