You can't call [Shield] unless opponents play attacks. [implications ... where's the sweet spot]
Maybe it needs to ability to also just call it for no benefit at the start of your turn or something.
These thoughts were going through my head as I was thinking about the on-play ability. I would prefer a Shield that only lets you take it off the mat when your opponent plays attacks, though balancing the on-play becomes really tricky.
Taking it off the mat: it could also just be discarded?
A cantrip Reserve Moat is probably too strong (you could argue that Shield's on play is situationally weaker than a cantrip). I think there are two principal ways to fix that. Either make the Reserve Moat terminal, e.g. a terminal Silver, or creation some interaction, e.g. a split pile with the Reserve Moats on top and some Attack card underneath and the Reserve Moats have to be called and trashed to defend.
Most attacks are terminal; if I make it a terminal Silver, defending against most attacks will cost the same terminal space as playing the attacks, but Shield will be cheaper than most attacks. That seems okay. Also,
Duchess and
Embargo are terminals Silvers for $2 with a benefit—but
Mountebank is also a terminal Silver with a benefit and it costs a lot more. Eh, the other attack-blockers cost $2, pricing Terminal Silver Shield at $2 is probably a fine place to start.
Speaking of other attack-blockers, I didn't even compare Shield to Guardian. Meh, Guardian is pretty similar to Lighthouse.
[Which attack to play first, whether to block weak attacks or not] Good choices to make.
Oh that's really cool, I hadn't considered that!
[Boons?!]
Moat, Lighthouse and Guardian all provide some small benefit beyond blocking attacks. Boons are small benefits, and there are boons whose benefits are pretty close to exactly those of Moat and Lighthouse. Oh hey, this is also true of Shield. That's really all.
I said that Moat
nets you +1 card. Actually you get +1 card twice (gross) and with Lighthouse you get the $1 twice and +1 action only once, so it's not exactly like getting two boons in both cases, but it's close.
[Idea: split pile]
I'm sure one could design a great Reserve moat split pile. In the case of Shield and my one other design, I've tried to make cards that would fit into a single canon expansion; split piles and Reserve cards have not (yet) appeared in the same expansion. My particular aims are really the only reason why I wouldn't do that, and now you know I have those aims
Anyways, let me just write up the revised idea:
Shield, RevisedAction — Reserve
Cost:
+
Put this on your tavern mat.
—
When another player plays an Attack card, you may call this. If you do, you are unaffected by that Attack.
At the start of your turn, you may discard this from your tavern mat.
With the other unmatting mode, the phrase that comes to me is "At the start of your turn, you may call this", and it's not obvious that "if you do, nothing happens" is implicit—it sounds like someone forgot to write the "if you do" part.
I like this version of Shield too. Great inputs, guys