This set is smaller than most other sets both because it is a Universes Beyond and because its not meant to be a full draftable environment
The problem here is that while blue and black don't overlap much in actual mechanics, they have a lot of abilities that are close to the other but just a little different
Set Booster Contents Set boosters have 12 cards , and theres a guaranteed rare or mythic card
Cards Between $5-10 The Fire Crystal Sword of the Animist Three Visits Primeval Titan Yuna, Grand Summoner Dark Confidant The Wind Crystal Jodah, the Unifier Genji Glove Nibelheim Aflame Loran of the Third Path Cryptic Command Aettir and Priwen Walking Ballista Command Beacon Tifa, Martial Artist The Earth Crystal Reanimate Y'shtola Rhul Ultima Weapon Cards Between $10-15 Dark Ritual Isshin, Two Heavens as One Tymna the Weaver Azusa, Lost but Seeking Diabolic Intent Vial Smasher the Fierce Lightning, Army of One Summon: Knights of the Round Kinnan, Bonder Prodigy Starting Town Final Fantasy Promos, Alternate Art, and More Final Fantasy is chock-full of alternate versions, with most characters having two versions, 10 of them having three and Cid, Timeless Artificer having 15
Despite all that, its a really strong and viable card for any last-ditch efforts
If you mean 'challenging' other characters, or glimmers, in play Steel and Ruby are good at challenging and can get benefits for banishing opposing characters during challenges
