Deny Reality

Bouncing a permanent is one of the weakest things five mana can do; the bounce here is almost beside the point. The real engine is cascade, which turns the casting cost into a likely free spell worth four or less off the top of your library. That coupling is the whole design logic: pay the full Dimir price for a tempo play that would normally embarrass you, and the cascade trigger refunds the investment with whatever lands first under the cost threshold. The bounce is intentionally generic (any permanent, including your own) precisely so the card stays flexible enough to justify the cascade attached to it; a more pointed effect would have warped the casting rate. Within the cascade family it sits among the cheaper triggers, which matters because cascade only hits cards strictly cheaper than the spell that carries it: at five mana, the floor of what you flip into is wide, while a two-drop cascade spell would be reaching into a much shallower pool. The friction built into the keyword keeps it from being a pure free roll: you exile until you hit, you may cast the result, and everything else goes to the bottom in random order, so the card rewards a deck whose curve is deliberately stacked to make that hit reliable rather than a coin flip.