According to the lore text at the bottom of the card, the creatures are trapped on a rock (possibly an asteroid.) Someone left behind an encrypted log recording the existence of slivers, either an unlucky explorer or, perhaps, a scientist involved in experimenting with the creatures, which would be a nice callback to the Riptide Project
The rest of the deck is fully on theme, as even a good amount of the removal in the deck creates a zombie in one way or another (Enter the God-Eternals, Syphon Flesh, Cruel Revival)
Jesus, this was a bit nerdy even for me, and I once wrote a post about Richard Garfield's PhD thesis
P/T Number 315 Language English Legal Formats Brawl, Commander, Competitive Brawl, Historic, Legacy, Modern, Pauper, Pioneer, Timeless, Vintage Not Legal Formats Alchemy, Standard Rulings (2/5/2021) Three creatures share a creature type if there's at least one creature type all three have, no matter what other creature types they have
Spike hits all of the needs, and thus is a major home-run from where Im sitting