Nahiris -10 is a fun achievement to pull off, but its not a necessary part of the card
While this would not be a problem if it instead serves the higher purpose of a game-ending combo, such as Sigardas Aid, I think Ephemerate does not quite do that
Enchantment Fall of Gil-galad (As this Saga enters and after your draw step, add a lore counter
Sol Ring and Arcane Signet are included in every preconstructed deck now, and will almost certainly improve any deck
Case of the Gateway Express White aggro decks have cheaper removal than a Hobbit's Sting, but Selesnya enchantments in Standard might add a few of these to supplement their Ossification package with Calix, Guided by Fate (am I the only one who only ever sees Freddie Mercury here?)
We want Commander games to be decided by who casts the best big spells, and Prime Time easily tips those scales