Of course, Im certainly no pro, and I generally dont play the Modern format that this set is largely designed around, so I cant speak to the exact power level of the individual cards here without inevitably making a fool of myself
(Each and/or in the mana costs of permanents of control counts toward your devotion to those colours.) At the beginning of each opponent's upkeep, this deals 2 damage to that player unless they sacrifice a creature
Blue will bring the ability to draw enough cards to keep going and return annoying permanents to your opponents hands, black brings with it graveyard tutors and the ability to return permanents from your graveyard to the battlefield and green gives us removal pieces to deal with some common graveyard hate effects, plus some of the heaviest hitters in the format that are worth reanimating
Your library stops being a creature, so it leaves the battlefield and goes back to being a normal library
As you get towards to more control style of deck the types of thing you want are more numerous
In its base state, a Blood Token can be used to improve your card selection