Release Date
Then if you have no cards in your library, exile this enchantment and put five cards from your graveyard on top of your library in any order
So you could spend five colorless mana to cast it, or one of each color, or literally a thousand different mixes of colored and colorless mana
Move along
Competitive Brawl Ajani, Nacatl Pariah // Ajani, Nacatl Avenger Lutri, the Spellchaser Nadu, Winged Wisdom Oko, Thief of Crowns Old Stickfingers Ragavan, Nimble Pilferer Rusko, Clockmaker Tajic, Legion's Valor Tamiyo, Inquisitive Student // Tamiyo, Seasoned Scholar Wrenn and Six Though Competitive Brawl shares many features with its Historic counterpart, like 25 starting life, a commander, and a 99 card deck constrained by the commander's color identity, it has a unique ban list of ten extremely powerful, oppressive commanders
Maybe they were of the same creature type, or showed a similar creative element, or just played well together