Even the Walls is a Sworn Sword Quest that is part of the Two Knights Taken storyline.
Even the Walls
"My [lady/lord], we will need eyes inside Harrenhal to watch the Boltons and their guests. May I instruct a sword to approach a suitable candidate?"
All Alignment Quests
Whichever option you select, the following Sworn Sword Quest will activate:
[Your Sworn Sword] successfully slipped Maester Lucas' poultice to Jaime Lannister. The Kingsguard is grateful for your aid and promised a great reward.
[Your Sworn Sword] was caught by Bolton forces trying to sneak into Harrenhal. The sword carries an angry raven back to you from Lord Bolton himself. (+1 Wound; Must Retry)
|Trail of Blood||-||Two Knights Taken - III|