The Good Of all the face commanders, Y'shtola, Night's Blessed is my pick for the overall most powerful if properly built around: it's an absurd card draw engine and finisher and lifegain all rolled into one
You can treat a learn card as a card that has some minor value effect like draw a card or create a token that can tutor for a lesson card from your sideboard
Enchanted creature gets +1/+1 and has "Whenever this creature attacks, scry 1.") You don't choose a target for Spellbook Vendor's ability at the time it triggers
If you gain control of a cloaked card the status of the card does not change unless noted, if it was tapped, it stays tapped, if it entered play that turn it still has summoning sickness, and you may look at it as it stays face down even if you and your opponent know what it is
Most of the cards' other versions are only a couple of dollars cheaper, so even if you only have that version, it is still worth alot