Kalistocrat's Nightmare

You temporarily curse a creature so its touch lessens the value of coins it touches. While under the effects of this curse, whenever the target touches a coin of higher value than copper piece, that coin changes into a copper piece. The change takes place over the course of the following minute, allowing the target to interact with multiple coins before the effect of the curse becomes apparent. The affected coins are permanently transmuted from their previous material (typically gold or silver) into copper coins, though remove curse (which can affect up to 50 coins with a single casting) or a similar spell can restore them to their previous material.