I'm just wondering if anyone else knows what exactly the 'Quest' part means, eg [DWARF RANGER]: Quest. Forced: After one of your other (dwarf) units leaves play, deal 1 damage to one target unit or capital. Other cards have Quest written before their actions too, does this mean there is some other requirement to perform these effects?

A zone in italics, like on the Dwarf Ranger or say, Keystone Forge, means that the ability or effect that follows only functions in that zone. If the unit is in any other zone that effect does not function. Not to be confused with the Defenders of the Hold which is battlefield only meaning the card can only be played into that zone. Hope that helps. It is in the rulebook somewhere, I'm sure someone will quote a page number.  

Cheers, that answers it - i was half-way though another game & realised what it must mean, and you have confirmed it. That's something to think about...

Just for completeness, when a card states for example 'Battlefield only', as in the case of Defenders of the Hold, it means that you can only play it in that zone, not that the unit can only be in that zone. Namely, you can move the unit to another zone afterwards.

Really? How do you figure that?

From the Rules, PAG 16

"Some cards have keyword restrictions that dictate the
zone into which the card can be played (or put into
play). When these cards enter play, they can only do
so in one of the specified zones. Note that this keyword
only restricts the card when it enters play, it can
then be moved (through card effects) to another zone."

This helped a lot. I had this issue during the last game and couldn't "decide" what "Quest" meant.

Also, DB_Cooper's explanation proves that you can actually move unites with, for example, "Battlefield Only" with cards like Imperial March ;)