The Watcher in the Water is a favorite scenario of many in this community, and contains some of the most annoying enemies I have ever had the pleasure of facing. With those dastardly tentacles whipping around and frustrating defender and attacker alike, it is risky to even attack them. Nightmare mode exacerbates this further still. A while back, I built this direct damage deck for the occasion!
Early on, we want to see a Gondorian Spearman and Spear of the Citadel in hand. Putting those two together with Thalin's help is enough to dispatch most of those tentacles, which commonly have 3 health. However, some have 4 or 5 health, so we have a few ways of getting the extra damage necessary. Fresh Tracks either ensures a 4 health tentacle will die or leaves a 5 health tentacle in the staging area to be killed off by Galadhon Archer or Descendant of Thorondor the following round. Sneak Attack is utilized for Gandalf, Descendant of Thorondor, or Rúmil so we can soften up a tentacle for our spearmen to finish off. The weapons included here are really just to ensure that we can likely play Straight Shot and Goblin-cleaver. Even Rain of Arrows and Pursuing the Enemy can help to finish off a group of tentacles. With Théodred's ability we will assist the other deck focusing on questing or we can apply it to Thalin when we need to bring out our more expensive cards.
This deck isn't only suited for The Watcher in the Water though, it can be used for any scenario where the enemies mostly have low health. While it is already capable of turning tentacles into sushi, additional cards in the future may enhance the options for doing direct damage and allow for more decks like this. In any case, traps aren't the only non-typical way to deal with enemies, there is also the way of the spear.