The Core set includes Grey Wind and Shaggydog as unique characters, and the Lords of Winter includes Grey Wind and Shaggydog as unique attachments. Can I have both versions of Grey Wind in play at the same time? What if Grey Wind the character goes to my dead pile - am I prevented from playing the attachment?

You can have only one Unique card with specific name in play so you can eighter have a character and then you can use the attachment as a duplicate on it or you can play the attachment first so that means that unless you get rid you the attachment you cannot play the character, also you you use the character as a duplicate on the attachment.

Fortunately attachments go to the discard pile, so you can still play the character afterwards.

I believe that if the character dies and goes to the dead pile, that will mean you cannot play the attachment.

Can someone please verify?

Fieras said:

Sure, here are the Core Set rules for uniques. Note that it refers to unique cards (which could be characters, attachments, locations, or events).

You also may not play or take control of a unique
card if there is a copy of that card in your dead
pile, or if your opponent has taken control of
another copy of that unique card from you.

Different versions of unique cards (i.e., cards
that have the same name but different stats and
effects) are considered to be the same unique
card (and thus only one version may be in play
on your side at any one time).