House Stark. No Leal.
Location. Coste: 1.

Old Gods. Winterfell.

Reaction: After a phase begins, sacrifice Winterfell Heart Tree to choose a card you control. Until the end of the phase, that card gains "immune to opponents' plot effects."

Cristi Balanescu
Wolves of the North #18.

Link: Decklists

Winterfell Heart Tree

Rules FAQ

Winterfell Heart Tree is a reaction to a phase beginning. First Snow is a Forced reaction to the challenges phase beginning, and Forced reactions always happen before normal reactions, so the Heart Tree is too late in that scenario.

If used in the plot phase, the Tree must be used **before** players choose plots. — mplain 211
Can this be used with the Withering Cold? Will the character stand? — Stathis 1
No. Withering Cold does not impact cards directly by causing them to stay knelt, but rather it impacts the game steps and simply skips standing. — scantrell24 3239
How does it interacts with valar dohaeris ? — Timmy 58
Whatever character you choose is immune. So you don't choose it to be kept for Valar D, but you keep it anyways. — scantrell24 3239