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
Dont let this name fool you, however
Trading cards have proven to increase in value over time, so it makes sense to ensure your cards are fully protected from any future potential wear and tear
DISDAINFUL STROKE When evaluating a counterspell, the biggest consideration is how its mana cost will line up against the cards its countering
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it even rebuilds well after a board wipe since you just need to play this and another cheap creature to get four or five counters at once