Heh, I designed this as a sorcery, Repurpose... urk, 4 years ago?! Was it really that long ago? Over 3 and a half years, I guess...

Anyway, yes, a instant does allow for a lot better use as a combat trick.

Nice. A simple solid variant on both green-buffing and Naturalise.

And the stories it can tell of "Ok, my creature blocks yours; steals and melts down your warhammer to make a shiny new sword..."

The problem with this ability is that the creature would be destroyed by damage before the trigger resolves.

They do usually take care to stop them being dropped first or second turn, though. This cycle feels a bit too strong.

But mainly it's the fiddly bit that gets me.

"You have to consider that outside of the block format, the drawback will mean next to nothing." - Depends on what mace20's aims are. If s/he isn't aiming to create a set intended to play with other cards, then that doesn't matter so much.

"Still has the problems of being a perfect dual land with a small downside which is only appreciable at top levels of play" - I'm not sure that's a big deal. Between cycles like Seachrome Coast and Glacial Fortress, there are plenty of duals with extremely minor drawbacks these days. (As I said on Forested Ravine though Wizards would print them at rare.)

Wording something like "Exile a card from your hand; you may play it as though it was in your hand"?

That does fix the speed issue - but it also powers this up still further by allowing you to choose what to reveal (so giving away nothing the first couple of uses) - or if still a random choice of what to perma-reveal, isn't faster but does slightly power it down by preventing revealing the same card over and over (by chance in the initial version)

Dunno; doesn't feel like the right way to do this. How about going simpler: "~ ETBs tapped unless you reveal your hand."

Still has the problems of being a perfect dual land with a small downside which is only appreciable at top levels of play.

how about reveal an unrevealed card from your hand, it stays revealed as long as it's in your hand.

As mentioned on another land you made - the random part is also a huge slowdown in gameplay.

Every turn I'm going to shuffle and offer my hand to the opponent 2 or 3 times? No way is that sensible.

Making knowledge of hand even more important sounds like a great idea. But for both power level and "Too annoying to live" reasons, this doesn't seem the bet way of going about it. I advise finding a different path.

"Reveal your hand" addresses most of the speed problems (still slow the first time, much faster after that) but no the power level problem.

You have to consider that outside of the block format, the drawback will mean next to nothing.

mace20: It's the "at random" part that's annoying. How about ", Reveal two cards from your hand:"? More knowledge at first, but you can keep showing the same 2 cards turn after turn.

Also, as duals that can produce either colour mana on turn 1, these would be rare by Wizards' design standards. (They'd be absolute staples in constructed, where your first spell likely gives away 50% of your decklist anyway.)