I think it would be interesting to implement some strange creatures:
Morlock (Common, 4R, Beast)
Attack: 4+N
N=#of morlock cards in game.
Morlock Lord (uncommon, 22R 12G, Beast, Alliance)
Attack: 10+2N
N=#of morlock cards in game.
Discards your hand, next cards will be morlock.
Troglodyte (Common, 6R, Beast)
Attack: 13
If there is a Soldier cards in game, attack=7
Troglodyte Queen (Beast, rare, durable, 5R, Quick)
Select a card from your hand to be replaced by Troglodyte.