Pointed Discussion

This card is quite beneficial in certain situations. Having it become a creature is very easy, especially when played against aggro decks. But where the real usefulness comes from is the ability to have it withdraw back into an enchantment when it comes under the threat of getting killed. Burn spells, destroy instants, creature damage; none of it will work when you can turn him back into an enchantment for nothing. His only downside would be that if the opponent doesn't cast creatures often then hes not going to see play a lot but instead will be forced to do nothing as an enchantment. His other weakness is that he's only a 2/4, not really all that powerful. My solution to that problem would be to play this guy with Doran, the Siege Tower to give him a power boost (need I really inform most player of such an easy combo?).

Run with Wrath of God, so glad they made this a Soldier.

Run with Kraj. Then you can make Kraj into an enchantment.

@Kryptnyt: Very interesting use for it, but what purpose would that serve?

@J***Aurelius

It has a couple uses, though it becomes a bit of a 'build around' effect. There are a few ways to give all your enchantments hexproof or shroud (Greater Auramancy,Privileged Position, Sterling Grove, Fountain Watch). This would allow your Kraj to take advantage of that protection without turning all of your permanents into enchantments (Enchanted Evening). It protects him from all direct damage and creature destruction/exiling effects at the expense of making him vulnerable to enchantment destruction. Hard to say whether or not the trade-off is worth it, but in the right deck, perhaps.

A 3 mana 2/4. Doesn't seem too bad. Protects itself.
Pretty nice
3.5/5

3-mana 2/4 with uncounterable regen. Me likey.

With the advent of enchantment creatures in Theros, the oracle text on this one should be changed due to the fact that a permanent can now be a creature AND an enchantment at the same time. The second ability should now specify that it's no longer a creature when turned into an enchantment.

It should say:
When an opponent casts a creature spell, if Opal Acrolith is an enchantment, it becomes a 2/4 Guardian creature with "0: End this effect.". (When you end this effect, it turns back into an enchantment and stops being a creature.)

@acolyte_of_night: the reason that this is either a creature or enchantment but never both was never because enchantments and creatures are exclusive; its because both effects are replacements effects. Blood Moon prevents nonbasics from doing things other than tapping for {R} because it changes them into a Mountain, not into a Mountain in addition to their other land types (like Urborg, Tomb of Yawgmoth). Likewise, Opal Acrolith turns into a creature, not "a creature in addition to its other types" and back to an enchantment the same way.