I had never tried Permafrost until about a week ago, and now I can't believe I mined without it. I have 2 of them in my deck and 1 bonewall, and it is working out great.
I've tried Permafrost Shield for a couple of games. Didn't seem to make too much of a difference to me. Maybe I need to try for a few more games, but...
Permafrost Shield is very expensive, costs 7
. The unupgraded rainbow deck, without Supernovae, cannot gather a lot of quanta very quickly, so if you're unlucky it would be mid-game until you can play that shield, at which point, more often than not, you'd be dying. In Puppy's FG killer, the deck size is very small and it has 6 Supernovae, which means it can draw the Permafrost Shield fast and play it quickly, thus utilizing it effectively. But for a larger deck without Supernovae, you can't use the shield effectively, and more often than not it'd be dead weight.
But again, Bone Wall unupgraded costs 7
. Maybe I need to drop a few cards in my deck and put in the Permafrost, to see how it works out.