8-Rack style decks benefit from a straightforward plan that's hard to interact with: Use discard effects to impair whatever our opponents are doing, coupled with cards like
The Rack that provide a quick enough clock to bring the game to a close once we've put them in "topdeck mode" and our discard spells are no longer good. Our
Rack replacement is our four uncommons,
Davriel, Rogue Shadowmage because he pulls double duty as a source of discard himself, and because uncommon planeswalkers are cool.
Without a lot of options at common for effective boardwipes, we need something to stave off aggressive decks that get their cards on the field before we can make them discard - especially since Davriel can be shut off simply by attacking him. Enter our rare, Noetic Scales, which does nothing to win the game but does make it pretty hard for someone to maintain attacks.
We need more win conditions than just Davriel for a deck with no to dig them up. A Spike would probably look for more noncreature win conditions like Corrupt since we're already planning on tamping down the board with Noetic Scales, but here in Johnnytown I'm going to opt for... zero power creatures! Perilous Shadow and Silent Skimmer will get the job done.
There's possibly an evolution of this deck that uses Glaze Fiend, The Rack, and artifacts that can become creatures, like Fountain of Ichor, but that may be getting a bit far afield. We'll try that version later.