To make this combo work while being FRIENDSHIP FOCUSED we are going to have to dig into the power cards~ Lets get down to business
You then choose an opponent at random
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
being an extremely repetitive "one-card combo deck" is problematic
Possibly devastating, possibly a complete dud
This arguably makes them the rarest cards ever and when one of them appeared at Heritage Auctions, a collector could not help but purchase it for $360,000