Walls of Umbar
The City of Corsairs Nightmare#4 (x2)
5 (4)
While Walls of Umbar is in the staging area, it gains: "Forced: After a player commits an ally to a Sailing test, raise his or her threat by 1.

*Forced: After Walls of Umbar is discarded from the encounter deck during a Sailing test, raise each player's threat by 1 for each ally he or she committed to that test.