The stat's were only there because I couldn't take them off, I couldn't find what layer they were on.
Anyway, I saw this more as a more permanent plague then I did as a fire shield knock off. The point remains that Skull Shield itself has nothing to do with the flavour of the game.
Perhaps make Necrotic Shield simply poison a creature, and have it cost 7
?
Then the upgraded would cost 8
, and prevent the one damage?
The reason why I'm loathe to take off the preventing of one damage, is because that protects any creature's with an attack of one from being poisoned. Essentially a backdoor around this shield if they have a good enough ability.