Thorough Investigation

Two mechanics welded into a single enchantment, and the weld is the whole design. Declaring attackers makes a Clue (once per combat, no matter how many creatures you send in); sacrificing that Clue draws a card and pushes you a room deeper into a dungeon. The elegance is that the two triggers feed each other. Investigate normally taxes you two mana and a sacrifice to turn a Clue into a card, but here the sacrifice is not a tax at all: it is the second engine's fuel, so you spend to draw and get dungeon progress along with it. What binds the loop together is that the venture is not optional. Cracking a Clue always advances the dungeon, one room per sacrifice, whether or not you wanted to be that deep this turn; the draw and the climb are bolted together, and you take both or neither. What paces the loop is mana rather than timing: each Clue costs two to crack (at instant speed, if you want to hold it as a bluff or convert it on someone else's turn), so a backlog of tokens cannot all cash out at once. You climb at the speed your resources allow, and the climb keeps coming as long as you keep drawing. It is a fair-value engine dressed as a combat payoff, converting the single combat trigger per turn into a slow, compounding draw-and-descend chain rather than an explosive one.