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
This is possible due to Poliwrath's Counterattack ability, which triggers automatically if this Pokemon is in the Active Spot
The card I actually like best on this list is Volraths Strongholdwith better creatures coming out each year, this utility land should never go down in price
The alternate art
There are 30 packs in each box
Grand Entryway // Elegant Rotunda is probably my favorite of these arts, but they all stand out just by how creatively they connect the two rooms together