Action: Until the end of the phase, each Rohan character with a Mount attachment gets +3

"Arise, arise, riders of Théoden!" –Théoden, The Return of the King

Sentinel.

While Erkenbrand is defending, he gains:

Response: Deal 1 damage to Erkenbrand to cancel a shadow effect just triggered.

Down from the hills leaped Erkenbrand, lord of Westfold. –The Two Towers

Sentinel.

They now learned to their joy that Erkenbrand had left many men to hold Helm's Gate, and more had since escaped thither. –The Two Towers

Response: After a Rohan ally is discarded from play by a card effect, ready Éothain.

"We must hasten south, lord. Let us leave these wild folk to their fancies. Or let us bind them and take them to our king."
–The Two Towers

Each hero with an attached Mount gets +1

Each hero with an attached Mount gets +1

Each hero with an attached Mount gets +1

Ahead nearer the walls Elfhelm's men were among the siege–engines, hewing, slaying, driving their foes into the fire–pits.
–The Return of the King

Action: Spend 1 resource to ready Ceorl. Then, you may give control of Ceorl to another player. Any player may trigger this action. (Limit once per phase).

He drew himself up. Then he knelt, offering his notched sword to the king. "Command me, lord!" he cried.
–The Two Towers

Sentinel.

Response: While Déorwine is defending, spend 1 resource to cancel a shadow effect dealt to the attacking enemy. Any player may trigger this action.

While a side quest is in the victory display, Rider of Rohan does not exaust to quest.

"Who are you, and what are you doing in this land?" said the Rider, using the Common Speech of the West...
–The Two Towers

Response: After Riddermark Knight is declared as an attacker, it gets +2 for this attack. At the end of this attack, discard Riddermark Knight.

Attach to a Rohan hero or Merry. Restricted.

Response: When a character leaves play, if that character shares at least one trait with the attached hero, exhaust Horn of the Mark to draw 1 card.

Then Éowyn gave to Merry an ancient horn, small but cunningly wrought all of fair silver with a baldric of green.
–The Return of the King

Action: Discard Rohirrim Scout to choose a non-unique enemy in the staging area. That enemy does not make engagement checks against you this round.

Swiftly a scout rode back and reported that wolf–riders were abroad in the valley...
–The Two Towers

While paying for The Muster of Rohan, each Rohan hero you control is considered to have a icon.

Planning Action: Search the top 10 cards of your deck for up to 4 Rohan allies and put them into play. Shuffle your deck. If any of those allies are still in play at the end of the round, discard them.

Response: After Westfold Lancer quests successfully, discard it to choose a non-unique enemy in the staging area. Deal 2 damage to the chosen enemy.

...the white fury of the Northmen burned the hotter, and more skilled was their knighthood with long spears...
–The Return of the King

Sentinel.

Reduce the cost of the first Rohan ally you play from your hand each round by 1 (to a minimum of 0).

"Arise now, arise, Riders of Théoden!" –The Two Towers

Combat Action: Ready Háma. He gets +3 until the end of the phase. At the end of the phase, discard Háma. (Limit once per round.)

"I am the Doorward of Théoden," he said. "Háma is my name." –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

Setup: Reduce your threat by 3.

Action: Raise your threat by 3 to ready Éowyn. She gets +9 until the end of the phase. (Limit once per game for the group.)

"But no living man am I! You look upon a woman. Éowyn I am, Éomund's daughter."
–The Return of the King

Combat Action: Discard Grimbold to choose an enemy engaged with a player. That enemy cannot attack that player this phase.

Grimbold's men turned aside and passed round to a great gap in the wall further eastward.
–The Return of the King

Permanent.

Setup: Attach to a hero.

Attached hero gains the Rohan trait.

Attached hero gets +1 while attacking with another Rohan character.

"Rise now, Meriadoc, esquire of Rohan of the household of Meduseld!"
–Théoden, The Return of the King

Response: After Éomer commits to the quest, spend 1 resource from his resource pool to immediately declare him as an attacker (and resolve his attack) against an enemy in the staging area.

...he was young, and he was king; the lord of a fell people.
–The Return of the King

Action: Spend 1 resource from a Rohan hero's resource pool to put Elfhelm into play from your hand under your control. At the end of the phase, discard Elfhelm if he is still in play.

"...my lord sends word that we must set ourselves in readiness; orders may come for a sudden move."
–The Return of the King

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.