The second idea is also very, very powerful, and nearly broken if it can stack. 2/3 extra defense for 3 quanta? That's a steal. Especially considering how shields gain cost when their defense increases just by 1, you have an instant 3 bonus shield for only 3 quanta. Even when used in a non-:earth deck, assuming most shields have a defense of 1, nearly everyone would pay 3 
for 2 extra points of defense. This card would be even more powerful when coupled with let's say, fog shield or permafrost shield or mirror shield.
"Instant 3 bonus shield for only 3 quanta"? You need a shield in the first place.
I'm considering having it just 1 DR, 2 if
mark, but that may be too large a bonus to Earth. Or, maybe it could only increase the DR of shields that already have DR, unless your mark is
.
This as it is now is probably a bit OP, the starting DR isnt really that big if a factor. If it could work with mirror shield, (It doesn't target) you can stop a large amount of decks.
What if it scaled. so each point of DR costs 3HP* current DR.
so you play a titanium shield. armagio, then this.
25HP
25-6=19 DR now is 3
19 -9=10 DR is now 4
10-12<0 DR is now 5
Interesting. Perhaps the card text could just say 'Sacrifice target creature to increase your shield's damage reduction. Higher HP creatures increase it by more.', and then a balanced formula can be worked out.
