This weekend's design challenge: Design a rare that inspires someone. Whether to include it in an existing deck of theirs, or to make a new deck around it, that's up to you.
Before you start the design challenge, I'd like to take a moment of your time and explain why I chose this challenge specifically.
Every card in a set does have to serve a purpose for the set, but it's also important for cards to strive to have purpose outside of a set as well. Over the years we've worked on Tesla, and the months we've been striving to perfect this iteration, many of us have gotten a good sense of 'needs' our set has, and what cards will fulfill them. But as this sense is honed, and cards get more and more specific usages in Tesla's limited environment, we begin to lose sight of what makes cards exciting outside of that environment as well.
It's important that we include cards in Tesla that reverse this order of priorities - cards that players will look at and immediately imagine using outside of Tesla, but that also have a subtle purpose within the set as well.
For one, we need to have cards that inspire deckbuilders. Cards that a player will look at and think, "I should build a deck around this", or, "I know just the deck that needs this."
And for two, if every card in Tesla has an obvious role in its Limited format, then it'll become a shallow format. Some cards need to have lenticular roles - an obvious use and a hidden use - and others need to be more subtle. Cards like Panharmonicon in Kaladesh are a good example of that: a build-around rare that excites players in many formats, and has more subtle synergies with Kaladesh itself.
I recommend to design a card for yourself. What card do you wish existed, whether for an existing deck of yours, or to make a new deck? Design that card, and then find a way to put a subtle Tesla twist on it. (This is how I designed Furtive Mage.)
And a reminder: we have room for one double-faced card in each color at rare! So feel free to design double-faced cards, but not too many!
Best of luck, designers! I look forward to seeing all of your designs.