Reprinting assemble a contraption cards seems fraught, and contraptions aren't likely to end up in standard, but how likely are new assemble cards to show up in a supplemental set?

Sadly, not very likely.

I've always wondered about Contraptions - you stated at the time that they weren't given borders with the intent that they would be black-border legal even though there were no black border assemble effects. But at the time dice rolling wasn't black board, and there are a number of contraptions that roll dice. Were you anticipating dice-rolling becoming black border back in Unstable?

I thought it was potentially possible.

“If an asteroid was headed towards Earth, and we were all surely doomed in a couple of months, would you tell us what the next alphabet worth of sets is about?” I would — well if that what’s it’s gonna take then I’m going to assemble a rag tag band of convicts led by Bruce Willis on a mission to make an asteroid hit us! You’re welcome, people of Earth!

If I’m responsible for the Earth getting destroyed, it’s going to reflect badly in my year review. (“Mark has done excellent design work this year, but that was overshadowed by his destruction of all the players.”)Trivia question: What card has a ruling telling you not to destroy the Earth?

The Most Dangerous Gamer made me really appreciate having a devoted legendary creature that enables attractions. Is it possible to get a devoted contraption legendary creature? My biggest struggle would be asking what color combination it should be. I don't want to be greedy and ask for a 5-color one, but I don't know which color or colors to skip.

If I had Unstable to do again, I’d make a legendary creature that could repeatably assemble Contraptions.

Does a non-creature artifact that has been temporarily enchanted into a creature, or a crewed Vehicle card with itself in its art, qualify as an "artifact creature" for the sake of Assembled Ensemble?

Assembled Ensemble only looks for an artifact creature in the art of a creature when it’s cast. It having the picture of something animated on the battlefield doesn’t make the object in the picture animated.

Resending this since it might have gotten lost:If I open a Unstable with Opening Ceremony during a game of Unfinity Limited, and cast a creature that Assembles a Contraption on that turn, can I Assemble one of the Contraptions from the pack on that turn? Or is that not close enough to Casting to work?

If you assemble an Contraption, you can make a Contraption deck out of the two cards in the booster and randomly draw one.

Hi Mark! Un Rules question: I know Assembled Ensemble is an Un card but how do you determine what is an artifact creature based on the art alone? Does Disenchant from Tempest count? The artificial sliver depicted in the set would imply that. Thanks!

There’s some common sense needed. In the case of Tempest Disenchant, the card show Hanna using Disenchant on a Sliver and the only one it would make sense on is the Metallic Sliver which is an artifact creature. Also, if you check Metallic Sliver, they look the same.

Silver-border rules questions! If I use Karn the Great Creator (brings an artifact into my hand from outside the game), can I get a Contraption? If I can, does it stay in my hand (with the wrong card back?), or go straight to the Scrapyard? If it is in my hand, what happens if I then find a way to cheat it into play? Does it go onto a Sprocket, or sit there meaninglessly? And if it doesn't go on a Sprocket, can I put it on a Sprocket with an "Assemble" ability? What about a "Reassemble" ability?

A Contraption trying to go to any zone other than the battlefield, instead goes to the scrapyard.

If contraption-assembling cards were eternal, would contraptions be eternal, too?

Yes. Contraptions were never silver border. If you could assemble them, you could play them. The problem was every card that assembled them was silver border.

Is it a game rule that all dungeons and all contraptions are immune to rotations? Can R&D change that so players can only use the most recently printed dungeons and contraptions?

Later cards could search for a subset if we wanted. For example, let’s say we return to Kaladesh and wanted to do Contraptions. We could “assemble Kaladeshian contraptions” which would only allow you to use a new subset. The old cards could assemble either since it doesn’t reference a subset.