Blindfold is especially strong in solo confuse/stun-lock decks: if you're reliably cancelling most of the villain's activations, then this is four rounds of knowing exactly what's coming. You can make focused plays that would normally be "risky", like leaving threat high for a round, if you know they're not actually risks! You can also choose not to apply stun on occasion, to control which cards are played as boosts vs reveals.

She's certainly best in Psylocke, who has both the built-in confusion and gets tons of value from Psionic and X-Men tags—but I also like her in other decks with divination tricks, like with Wiccan as Stretch22 said, or a yellow-green Spider-Woman where we leverage her alter-ego ability and tricks like Leading Blow to keep things reliably locked down.

Blindfold is an interesting ally that is quite good in X-men decks and fringe playable elsewhere. Thanks to the X-men support cards like Utopia and Danger Room, the bar is quite low for any X-men ally to make the cut in a dedicated X-men deck. Her ability is hard to quantify relative to other game actions but clearly powerful. You need to be mindful of what encounter cards will be drawn as boosts or as encounter cards, and how that changes when you remove a card, but it is a good way to delete a devastating boost effect or a card like Shadow of the Past. It can also help you decide whether you should enter the villain phase in alter ego or hero form, and whether you should tank or block the villain's attack. For example, if you are 3 threat away from completing the main scheme, but you know the villain's activation will only put 2 threat on, you can safely end your turn in alter-ego to get the extra hand size. On the other hand, you could be sure to end in hero form if you know a scheme would lose you the game. One thing I like is you can get all the value out of Blindfold in one turn cycle with a play-activate-block and clear up the ally slot right away, or you can put a Mission Training on and get lots of value over time. Shout-out to Wiccan as well, who always likes to know what's on top of the deck. Blindfold is an easy inclusion for any X-men deck, and with such a unique ability could be a role-player when fighting certain scenarios.