To me, being able to play the opponents card seems a bit OP. Can you imagine the frustration? It is basically bait for CC spells, coz if you don't use it it'll be used against you (or something worse).
Simply seeing someones hand and choosing to discard one, however, (the effective opposite of Precognition) appeals to me greatly
Though it does not seem very Entropyesque.
I imagine the idea was Entropy because Entropy is one of the staples of Rainbow (the other usually being Time). However, the original feels like an Aether card to me (Mindgate, or handgate??). It even resembles Spark.
And my suggestion (discard the card only, though to balance that it should probably be a spell), feels like Dark, or possibly fire (a hand deflag), though ironically, I think those are elements that could use it the least.