Here's how the deck looks with the upgrades added: Also to pre-emptively address some comments: one direction that you can take the upgrades is to really lean into Sliver Gravemother's encore ability and turn the deck into a straight-up Encore deck -- Buried Alive and Entomb cards to put slivers into your graveyard, Convergence of Dominion and Zirda, the Dawnwaker to make encore cost less (though PSA Training Grounds doesn't work, I see people suggesting it but sorry no), Mondrak, Glory Dominus to double the encore tokens, Sundial of the Infinite to keep the encore tokens permanently -- that sounds sweet and all but you'd need to do a massive rework of this entire precon, turning it from a Go Wide Sliver Combat deck to Sliver Reanimator essentially
Anthems that pump your team like Gaea's Anthem
Lillie's Clefairy ex is the most valuable at $231.52 as a Special Illustration Rare card
If heads, eat the other player
The ability has you roll a d6, and the result chooses one of four beneficial effects: creating squirrels to chase, digging up a spell from your graveyard, biting a player or creature, or earning a couple more rolls
Is Item Shopkeep legal to play