Rules FAQ:

• This is not a kill effect. The card is discarded, then placed from the discard pile into the dead pile. Reactions to a card being discarded from hand can trigger (e.g. Cersei Lannister (LoCR)), reactions to a character being killed cannot.

• If a unique character is placed in your dead pile while you have another copy of that character in play, the copy in play is not affected in any way. However, you can no longer bring other copies of that character into play as duplicates (see FAQ (1.2)).