Eerie Halls
The Treachery of Rhudaur #102 (x2/x1)
Location
5 (4)
Ruins.  

Action: Raise your threat by 1 to reduce the Threat of Eerie Halls by 1 until the end of the phase. (Any player may trigger this action.)

Shadow: If the defending player does not control at least 1 Clue objective, the attacking enemy makes an additional attack after this one.