The Rare that you'll find in the Jumpstart booster will always be relevant to the theme
Bigger, scarier threats dwell in the graveyard these days, but Inkwell still shows up in a lot of Cube Draft formats
Conspiracy (Start the game with this conspiracy face up in the command zone.) Your deck can't have basic land cards and your starting hand size is five
Instead, Mono-Blue often wins by drawing four cards, untapping three permanents, copying a spell, flickering an Artifact multiple times, and then saying, "I would like to present an infinite loop from here." And to help you get to that point in the game, a great Mono-Blue Commander should be able to give you repeatable value in one form or another
Nadu, Winged Wisdom Nadu, Winged Wisdom also enters broken territory, with ramp potential so unbounded that it almost immediately ruined formats and subsequently hit the banlist
Enchanted creature has "Whenever another creature dies, put a +1/+1 counter on this creature." When enchanted creature dies, look at the top X cards of your library, where X is its power