It is a staple in blue-based control strategies because it allows its controllers to play earlier card draw or countermagic while also getting a 5/6 creature at instant speed
Regardless, you can see where conniving can become a useful "special guest" mechanic on this creature
Brawl Legal Vintage Legal Timeless Legal Commander Legal Pauper Legal Oathbreaker Legal Penny Legal Toolbox Buy This Card Notes and Rules Information for Dark Bargain: If you have fewer than three cards in your library, you put them all into your hand and none into your graveyard
Box Contents by Rarity At a JPN box price of ~19,400 ($129): Singles vs Sealed Which Strategy
Raise At the beginning of your end step, if you gained life this turn, return target creature card from your graveyard to your hand
Moderation Unlike the rest of this list, Moderations spells-per-turn limit only applies to you