House Stark. Non-Loyal.
Character. Cost: 3. STR: 2.

Lady.

Stealth.

While Arya Stark has a duplicate, she gains a icon.

Reaction: After Arya Stark enters play, place the top card of your deck on her facedown as a duplicate.

Joshua Cairós
Core Set #141.

Link: Decklists

Arya Stark
Reviews

Rules FAQ

Arya's ability checks whether or not she has one or more duplicate(s). This is binary - you either have a duplicate or you don't have any duplicates. Provided she has one or more, she gains one Military icon.

Some abilities put cards into play facedown. A facedown card has no inherent attributes other than “facedown card,” but it may be granted attributes by the card ability that put it into play. A player may look at the identity of any facedown card that is in play and under his or her control.

I know as a new player, Arya was the card that taught me that cards that are played during setup are not "in play" and so the card's reaction is ignored. This may be a necessary rule, but it is a counter-intuitive one for new players, or at least I thought so. — treyalsup 7
If Arya enters play under your control from an opponent's discard or dead pile, you cannot trigger her ability, because you cannot duplicate cards that you do not own. (http://thronesdb.com/faq#Duplicates) — mplain 195

FAQ "Duplicates":

In order to bring a card into play as a duplicate, both the duplicate and the unique card that would be duplicated must be owned and contolled by the player attempting the duplication.

If Arya enters play under your control from an opponent's discard or dead pile (e.g. via Yoren or The Wall), you cannot trigger her ability, because you cannot duplicate cards that you do not own.

mplain 195