While Foothills of Mordor is in the staging area, 'when revealed' effects cannot be canceled.
Forced: After Foothills of Mordor becomes the active location, raise each player's threat by 2.
...there lay dark thickets, and a tumbled land of rocky ghylls and crags, behind which the long grim slopes of the Ephel Dúath clambered up.
–The Return of the King
While any player has threat of 35 or higher, Shadowy Vale gets +3
Forced: After Shadowy Vale becomes the active location, reveal the top card of the encounter deck.
...nothing could waft away the glooms and the sad mists that clung about the Mountains of Shadow...
–The Return of the King
When Revealed: Raise each player's threat by X, where X is the printed quest points of the active location. If there is no active location, Mountains of Shadow gains surge.
Shadow: Attacking enemy gets +1 
If this attack destroys a character, raise your threat by 2.
The path through the hills has led too far up, and now you walk along exposed heights where there's nowhere to hide. You need to find a way down.
Each player's threat cannot be reduced.
Response: When Find a Way Down is defeated, each player reduces his threat by 3.