Using the cards you picked during the drafting phase and as many basic lands as you choose, you then have to build the best 40-card deck you can
That doesnt put Black Mage decks in a great spot in current Pauper
Sliver Support There are a handful of cards that directly support Slivers, and then there are a bunch of cards that can support decks that have a heavily focused tribal theme: Hive Stirrings, Hivestone, Sliversmith, Cavern of Souls, Cover of Darkness, Kondas Banner, Packs Disdain, Shared Triumph, Standardize, Steeling Resolve, Unnatural Selection, Adaptive Automaton, Alpha Status, Descendants Path, Faces of the Past, Harsh Mercy, Luminescent Rain, Shared Animosity, Urzas Incubator, Call to the Kindred, Distant Melody, Door of Destinies, Mana Echoes, Riptide Replicator, Roar of the Crowd, Belbes Portal, Coat of Arms, Cryptic Gateway, Patriarchs Bidding, Vigean Intuition Changelings Lets also not forget that Lorwyns changelings are Slivers too
No downsides for you