4/19/2016 - Here are the other designs I baked up in response to last weekend's art challenge.
Looking at Agent of Death now, it's clear the simpler and more direct Stealer of Secrets homage would simply investigate when it hits. I'm not unhappy with the Night's Whisper element, but that it needs an 'otherwise' is a good sign it's doing more than it needs to.
Criminal Investigator isn't doing much new (see Ulvenwald Mysteries) but I'm happy with it both mechanically and thematically.
Here's the other path my submission could have taken. A good example of a more complex card being easier to understand.
It's got first strike—despite very placid art—because granting it +1/+1 per clue would allow opponents to kill it by spending their clues mid- or post-combat. Even if it only counted your own clues, players would occasionally kill it by accident.
I wanted to explore a gothic detective legend. This first pass is synergistic and flavorful, but treads on Criminal Investigator, above.
This second pass is more unique, and I like the way it gives clues new functionality that makes sitting on so many more palatable, as well as how it accelerates you toward the goal indirectly. But I'm not sure it'd be more fun the other version.
Pretty standard, really. (But it sure does enable madness well.)
This cycle was born because I wanted clues to be the thing that let you discover the secret truth of a card, like Westvale Abbey and Ormendahl, but achieved through investigation.
It would be really neat if I could play a Suspicious Monolith and you didn't know what was on the reverse side. Presently, all double-faced cards have a 1:1 relationship between the front face and the back face, but are we locked into that?
Associating one front face with multiple back faces might cause trouble for Gatherer or Magic Online developers, but that issue should be addressable with work.
The more immediate concern is how these would work in physical games.
With thick sleeves, it's no problem. You keep your card in the sleeve, and transform it only when you're ready.
With checklist cards, there'd be no way to unambiguously indicate which monolith is which while keeping the back side secret from your opponent. If they're all mythic, I'd be willing to hand wave that problem away for Limited on the basis that it will come up ridiculously infrequently, but that doesn't solve Constructed. The sleeves do, but we've never required sleeves before.
Ultimately, it's most likely not worth implementing. That doesn't mean the idea wasn't worth exploring.