I see this has been entirely reworked.
Lava giant, Uncommon, 10b10g
Burning; Unliving
Wall: -20
Attack: 15
If #Unliving in hand < 3 or #Burning in hand < 3
Tower: -10
Wall: -10
Um... so let me get this straight. You lose 10 bricks, 10 gems, and 20 wall just so you can deal 15 damage? Oh, and if you don't have three Unliving AND three Burning in hand (which you won't because these keywords do not mesh, even with this card), you're losing an additional 10 tower and 10 wall? What?
Shall I assume that you meant the opponent's wall -20? And do you really mean for the If statement to say "or" (meaning that having three of one isn't enough if you don't have three of the other), or did you mean it to be "and" (you can have less than three of one as long as you have three of the other)?
Otherwise, you're looking at 15 damage to the opponent at a likely cost of 30 wall, 10 tower, and 10 each of bricks and gems. Ouch!