I'm unclear on how I can get this card played.  In the rules for the Planning Phase it says that only during this time are you able to play Attachment's.  This card seems nearly impossible to play during that phase.  Was this card supposed to have some exception to the standard rule that should have been placed on the card or am I misunderstanding the rules?

Istm you get plenty of opportunity. If an enemy survives a round of combat then it will be considered to be engaged during the next round's planning phase.

Forest Snare is ridiculous good, and is pretty much the only way I've managed to win Scenario 2. Yes, if a nasty monster comes out you have to let it beat on you for a round, but this will let you completely nullify it as a threat.

So Monsters never unengage?  That would be where I was unclear.  So you really only deal with monsters hurting you on questing for 1 round before they engage (unless they are too high to engage you and you don't go and pull them), right?

Uthanar said:

Pretty much. There are a couple of exceptions like A Light in the Dark which lets you move an enemy back into staging or Wargs who sometimes run back to staging area after they attack you.