Duggan, Private Detective

The design here reads as a deliberate feedback loop between two axes that usually fight each other. A creature whose body scales with cards in hand wants you to hoard; the repeated investigate on enter and attack builds a stockpile you can cash back into that grip. The wrinkle is that the Clues don't grow Duggan directly: they sit on the battlefield as artifact tokens until you sacrifice them to draw, and only that draw feeds the power. So the engine has a valve. You bank Clues on your terms and convert them into hand size (and body) at the moment it matters most, rather than being force-fed cards you might not want. The activated ability is where the loop pays off: it deals damage equal to twice Duggan's power, and the power is your hand count, so a full grip turns a single tap into a removal spell that comfortably outscales most creatures. The one-time restriction is the discipline that keeps this from becoming a repeatable cannon: you get exactly one big swing, timed for when your hand is deepest, so the reward is front-loaded rather than grinding. What makes the assembly clever is that all three lines point at the same number. Investigate stocks the fuel, the draw converts it, the P/T reflects the count, and the punch multiplies it. The joke, quite literally, is that the longer you refuse to commit, the harder the detective hits when he finally throws it.