Without spoiling too much from each individual deck, I will preface this review by saying some of these decks introduce really cool new cards to Magic, but half-deliver on an exciting precon experience
Phyrexia: All Will Be One is a Phyrexian-heavy set (obviously) that continues the interdimensional (and time-traveling) war between the Phyrexians and the multiverse
As it turns out, there are a lot of popular Legacy cards that rely on spells that are cast for free

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It's heavy on non-inkable cards, which can make your early turns tense