I dabbled with this idea before, but I think it makes more sense as a permanent effect. It may be too good to be able to burn out chump blockers, but I don't think so, given that "target creature gains trample" is rarely given repeatably to arbitrary creatures, but is sometimes, and this requires an extra hurdle.

I'm... not sure what this card is supposed to be doing. My mind keeps translating this as "Unblocked creatures are unblocked.", but I'm pretty sure that's not the point.

Thats how I thought of it; I thought of it because I was amused by the wording. But I think it does fit the rules. The point is, if the creature blocking something is regenerated, removed from combat, destroyed or exiled then by default, the attacking creature remians blocked. An example of "what if the rules worked this random way instead" :)

I originally had it as "when... it becomes unblocked" but it wasnt as clear as the tautological-sounding version.

I've had a few tries at wording this in my set, too.

I think we ended up with: Blocked creatures with no creatures blocking them. Which is pretty close to yours :)

Ah! Yes. I felt like Id seen something like it, but couldnt find anything in search.

It was http://multiverse.heroku.com/cards/4356 The frumious

This is a very pleasing card. Initially looks useless, but is a bit more powerful than it looks: at the moment an aggro red deck has to decide whether to burn out blockers before attacking or not; this gives you the flexibility to wait. I like it.

My brain hurts.