They are all versatile and good for both set up and to start closing out the game
Voracious Bibliophile is some seriously good card draw, especially if you run spells like the TBD Intervention cycle, Curse of the Swine, March of Swirling Mist or Sublime Epiphany
Karn Liberated Karn Liberated is a difficult planeswalker to deal with
With the Mind Flayarrrs precon, we finally get some genuine support for this largely unsupported tribe
Dionus, Elvish Archdruid Dionus, Elvish Archdruid is absolutely disgusting in a Tyvar the Bellicose or Lathril deck, but they're still pretty powerful on their own
Any counters it has stay on it, any auras or equipment stay attached, and delayed triggers (like having to sacrifice it after using Wings of Hubris) still happen to it