Honestly surprised that there aren't more comments on this card, since it punches way above the power level that it reads. I understand what the designer is going for here; a tap land with a trinket effect on ETB that has deeply resonating flavor notes is a really interesting design, but the problem here is that looking at a player's hand isn't something that should be trivialized. Outside of cards that intrinsically need it to function (target discard and the like), the number of cards that staple on the ability to look at the opponent's hand are actually quite small. This is not a coincidence. The closest parallel that can easily be drawn to this card would be the much maligned Gitaxian Probe, a card that has been banned or restricted in many formats. Go read these ban decisions. The number one cited reason is trivialization of information. This card might not be as excellent in linear combo strategies as it is a tap-land, but in a lot of ways this card is more powerful. First, the opportunity cost on this card is very low. Decks are going to have to play dual lands to fix their mana. A land that simply produces two colors and enters tapped has been playable in many standard formats in the past. Decks in modern (like, say UW control) play lands that ETB tapped from time to time and are happy to do so. Imagine a turn where you have to decide to tap out for Jace, the mindsculptor, or keep open a counterspell. Tough choice, but with this handy land you wanted to play anyway, you now remove that facet of the game. Imagine this card played against you on turn one, after you spend a bunch of time thinking about your sequencing. Imagine you are playing a rogue deck and have this played against you and have your game plan spoiled. This card might feel whatever the first ten times its played against you, but sooner or later you are going to hate it. You will loathe that the opponent always has the answer to what you play, or somehow always seems to be one step ahead. This card is sinister. As a hobbyist designer myself, I really find a lot about this design appealing. Hits all the flavor notes. Feels UW. Great design space of ETB trinket text. That said, I strongly urge reconsideration on this card.

I understand the point. I guess I didn't think about the power level too much outside the context of this set (self-contained, and this card is a one-off in the duel deck).

Listening to your rationale and remembering the games that this card actually came up, I'm thinking of making the ETB trigger 'target opponent reveals two cards in their hand', which would reduce the power and give it a more interesting strategic layer of when to play the card to get the most use out of it.