I rarely venture out of the Card Ideas section of the forum, but here I am.
Bonewall has to be the top shield card in the game.
Simply for the fact that every time something/anything dies it gains protection from 2 more sources of damage. Now, my record has been 63 Bones on my Bonewall against Morte, I firewall him, and he plagued my skeleton army 4 times.
. What else makes Bonewall the top dog, is that it cannot be stolen or destroyed. Big plus.
I haven't tried Permafrost, doubt I will. Phase shield is, to me, 3 sundials rolled into one with no card-draw ability. I run steals to take whatever is shiny that the FG has (and I want), most notably a Dissipation field, late game, from Chaos Lord.