While reducing a creature's attack by half and making it immaterial is assuredly powerful, my main point against this card is that there isn't enough working with the "Buried" theme yet.
My effort to change that was in Crude Oil (http://elementscommunity.org/forum/index.php/topic,29059.0.html) and as you can see there is clear synergy in our card ideas.
Aside from the lack of in-game "Buried" theme I really happen to like this idea, and for Earth's defensive nature, cutting a creature's attack in half is a powerful tool to have for itself.
P.S. I think the costing of this card is adequate, especially considering that Antimatter can reduce a creature's attack value twice over for 8 , while this card reduces it by half.
Compare:
Atk reduction: -200% | Atk Reduction: -50% |
Cost: 8 | Cost: 3 |
-200% = -50% * 4
∴ 8 = [cost of Entrench] * 4
[insert Arithmetic], results in: [cost of Entrench] = 2
Due to Earth's defensive nature however, a little increase in cost seems adequate compared to pure elementally-ignored calculations. Therefore the cost 2 + 1 = 3 seems accurate.
@Frostguard: You seem to enjoy making card ideas a lot. Keep at it. You're doing excellently. Try to make the art for some of your cards, it can open the doors for you in a lot of ways. Kudos.
I've added another card idea which could have synergy with this card.
Also, your card idea is impressive, although I think the name Crude Oil doesn't really fit in the world of Elements. I'd rather call it Excavation | Excavation.