Judging by your terminology, I have deduced that you don't have much experience with the actual game. In that case, welcome.
Multi-element cards (as Zblader has stated) have been tried several times before (also by Zblader), and failed (Zblader again.
). Life cards traditionally grow and cause you to benefit, such as regeneration. Regeneration and Growth don't necessarily merit shield copying, however, cloning (like Mitosis) and reproduction could possibly fit. Maybe you could make a Darkness creature with the ability
Reproduce: Gain +0|+10, gravity pull, and the ability of the opponent's current shield.
When trying cards with multiple elements, the best way is to have a single element for the card itself, and a separate element for the ability.
When I think about it, it's almost like a reverse Crusader.