^ this version. Very nice.
Not sure if there will need to be a new line of code or two, to determine whether or not a creature = mutated.
I'm presuming that the effect of 'Mutated Creatures gain +1/+1' stretches to include Abominations, Micro-abominations as well as Lycanthropes and Werewolves?
Because, in theory, a lycanthrope mutates into a werewolf.
With the ability as an effect which causes the "50/50 to be or not to be an attack" it is much better.
My only problem is that; theoretically, it will cancel itself out.
Imagine 20 Skeletons attacking you, you play Dice Game. In a perfect statisticians world, 10 skeletons will deal 2 damage, and the other 10 will deal 0 damage. Therefore, you still take 20 damage as though each and every Skeleton attacked you once.
It is very much a risk. It's main use will be to play it when your opponent has a variety of low (1, 2 or 3) damage creatures and a couple (7, 8 or 9) damage high hitters. Then, there is a perceived chance that the effect might trigger on how low hitters, but cancel out the high hitters. But it is purely theoretical. In another instance, you might end up doubling the attack of 90% of your opponents creatures and only avoiding 10% of it.
The effect, therefore, in my mind - is useless.