House Stark. Loyal.
Character. Cost: 4. STR: 4.

House Tully. Lady. The Seven.

While Catelyn Stark is participating in a challenge, your opponents cannot trigger card abilities.

I take no joy in mead nor meat, and song and laughter have become suspicious strangers to me. I am a creature of grief and dust and bitter longings. There is an empty place within me where my heart was once.
Tommy Arnold
Core Set #143.

Link: Decklists

Catelyn Stark

The following FAQ is taken from The) Unofficial FAQ on the CardgameDB forums:

What does Catelyn Stark prevent?

Since Catelyn Stark prevents opponents from triggering card abilities, she does not prevent occurrences mandated by the game, like "Forced Reactions", "Forced Interrupts", and "When Revealed". Likewise, as she only affects card abilities, she does not affect duplicates - which are defined as a triggered game ability. Finally, she only prevents triggered abilities, so she does not prevent anything that lacks a boldface precursor (e.g. keywords like Ambush or Renown).

However, she does stop pretty much everything else - including events. Since the limitation Catelyn is placing is on the player, not the cards themselves, she's not "restricted" to only affecting cards in play.

agktmte 1486
how it works with shadow cards, and bring out of shadows, or ambush? can my opponent put in play or trigger his abilities?? — naitz 3
Catelyn only stops triggered abilities, i.e. abilities with the boldface precursor such as actions, reactions, and interrupts. However, she does not stop anything with 'forced', since that is the game triggerring the ability, not catelyn. — prancingPWNy 104