> "Target player reveals three cards at random from their hand and you choose one of them. That player discards that card."

Okay, so first of, the name has been used already: Mind Extraction.

Second, this is a strictly better Blackmail, which I at least personally see as a rather decent card so uhh.

Third, and the most troubling thing, is that this unlike usually discard cards of this nature, this can hit lands. That should be alarming to any designer I think. I've seen several custom designs in the same vein, and I recall this issue was brought up often with them - I don't remember if any good way to resolve it was found.

A basic scenario is that players tend to keep hands with roughly 2 lands in them, so if you cast this on the first turn and happen to hit one of their few lands, it can easily severely damage the rest of their game. Especially in constructed I would imagine it would be so warping that it might generally be preferred to construct your decks in a way that you can aim to keep three landers over the usually two-land keepers.