These were quite similar stylistically to lowercase ex and LV.X cards with a few notable differences
Learning from these high-level plays, even casually, provides immense insight into advanced strategy
Not cards that they didn't bring in ever because the right matchup never came up, but cards that even in the right matchup weren't going to be relevant
Less utility for more immediate impact and safety against being attacked to death
Graveborn Muse has the potential to be several Phyrexian Arenas taped together (although watch out in Zombie decks that it doesn't kill you), and Underworld Connections is basically a Phyrexian Arena that just asks you to sac a land when it enters
It has solid stats as well, and if you're playing cards that keep the tokens from myriad around, like The Master, Multiplied