Its Ability, Princesss Curtain, prevents your opponent from using the Effects of Supporter cards on your own Benched Pokemon
Cards that play into this style of play are working towards the larger goal of decimating the opponent's hand, and usually then punishing them for having no cards
UGIN, THE INEFFABLE New-gin, as I like to call him, is akin to a ritual in equipment builds
Lets sift through about 450 scry cards in Magic and pluck out the best of the bunch
As of now, its a good Ability that works well with the high-Energy metagame, but not with the low reliance on effects of attacks
Combine that with only 2 PSA graded copies in the database, and you can see why it fetches so much at auction