One thing this has on Goblin Dirigible is that it avoids sorcery-speed removal.

I guess it's only a common - but yes. Pay 5 mana a turn for a 6/4? And 6 mana one off on top of that? Why wouldn't I run a Craw Wurm and only pay the 6 and no upkeep, and not risk my land? And that's not exactly a top-tier level of card nowadays.

I mean.. sure, this is arguably better than Giant Slug...
And, looking deeper - the closer comparison is probably Goblin Dirigible. Which is slightly smaller, but cheaper to activate, and flies. I guess it depends how much you cost flying vs 2 power.

And, as a complete aside, because I found it while looking for cards with high upkeep: Kuldotha Phoenix looks like a giant firey foot. Sorry, bet you can't unsee that now.

I think there is a nice idea here, that right now doesn't work. Why would I want to pay for a 6/4 creature every turn, if instead I could put that mana to good use to pay for other permanents? This doesn't improve my board state at all. However, if the Golem did something interesting, that was really worth paying 5 mana over and over, I think this could be an amazing design space! You'd have to calculate if your mana should go to the cool Golem again or if you use it for something different. Maybe giving the Golem annihilator, or every time you attach it to something, you put a charge counter on it, and for every charge counter it'd animate another land?

­Faith Unbroken brings the "O-Ring Aura" even closer to this, though they still have it at uncommon.

Ironically, Outnumber adds to the general condemnation of Dogpile. I mean, sometimes, limited is happy for any burn, and even a situational 1 or 2 for 4 is worth playing. But boy, that Dogpile was below the curve. Outnumber is starting to look about right -- situational, but good in many circumstances.

The best line I've heard about Void Winnower?

Your opponent literally can't even.

And wizards have kept the ball rolling with Void Winnower (see http://magic.wizards.com/en/articles/archive/command-tower/void-where-prohibited-2015-09-10 ) bringing the reminder text "zero is even" back to magic :)

Indeed!

Nearly realised by Gilt-Leaf Winnower ! :)

Looking at it now, a few months later, these do look pretty confusing for commons. The fact that you get to use these at least twice per turn cycle makes them different to most tap abilities out there, with the exception of Cinder Pyromancer and similar. It also makes them hard to make look attractive, because this looks merely okay but I think this is actually overpowered at the moment - an unstoppable drain of 2 life per round plus a 2/3 blocker.

The discussion over on Gold uncommon submissions originally suggested that the off-colour uncommon activations could have Enlighten-Untap. I think having mocked up and looked at these three examples, I prefer the idea of Enlighten-Untap on uncommons than on commons, and on effects with mana costs to on effects without.