Play only after the resolving enemy attacks step is complete.

Combat Action: Exhaust and discard a Rohan ally you control to choose and discard a non-unique enemy engaged with you.

"Helm is arisen and comes back to war. Helm for Théoden King!" –Riders of Rohan, The Two Towers

Response: After a Rohan ally you control is discarded from play, exhaust Gamling to return that ally to your hand.

"...we have a thousand fit to fight on foot," said Gamling, an old man, the leader of those that watched the Dike. –The Two Towers

Attach to a Rohan hero. Restricted.

If attached hero is Théoden, Snowmane loses the restricted keyword.

Response: After attached hero quests successfully, ready attached hero.

Suddenly the king cried to Snowmane and the horse sprang away. –The Return of the King

Sentinel.

Response: After Beregond defends an attack and takes no damage, reduce the defending player's threat by 1. (Limit once per round.)

“The Lord does not permit those who wear the black and silver to leave their post for any cause...”
–The Return of the King

While there is a hero in your discard pile, Prince Imrahil loses the ally card type and gains the hero card type.

"We must gather all of the strength that we can find.
–The Return of the King

Response: After a sentinel character is declared as a defender, it gets +2 for this attack. If this attack deals no damage, ready the defending character.

...but alone in the porch upon the topmost step stood Beregond, clad in the black and silver of the Guard; and he held the door against them.
–The Return of the King

Attach to Gondor hero. Restricted.

Response: Spend X resources from attached hero's pool to cancel X damage just dealt to attached hero.

This was the livery of the heirs of Elendil, and none wore it now in all Gondor, save the Guards of the Citadel...
–The Return of the King

While Elladan is in play, Elrohir gets +2

Response: After you optionally engage an Orc enemy, ready Elrohir.

"From the North we came with this purpose, and from Elrond our father we brought this very counsel."
–The Return of the King

Galadriel cannot quest, attack or defend. Allies you control do not exhaust to commit to the quest during the round they enter play.

Action: Exhaust Galadriel to choose a player. That player reduces his threat by 1 and draws 1 card. (Limit once per round.)

Action: Discard 1 card from your hand to give Éowyn +1 until the end of the phase. This effect may be triggered by each player once each round.

Action: Discard a card from your hand to add 1 resource to a Noldor hero's resource pool, or to Aragorn's resource pool. (Limit once per round.)