It should be that every clear awards a guaranteed drop, such as a Midan Cog (for Alex Midas). 20 Midan Cogs should be tradeable for whichever tarnished Midan item that you would like to purchase. This requires effort to be put into earning your drops, but also ensures that with the right amount of effort you will be rewarded by receiving the drop you were after even if you had really bad luck with RNG.