In practice I think different colours gain more or less from lessons more as a result of their colour pie and cube archetypes
Without paying their mana cost is important considering you already pumped 7 mana into Etali
Then, if you sacrificed an Artifact, enchantment, or token when casting this spell, you get to put them directly into play
The list includes favorites like Gemhide Sliver, Harmonic Sliver, and Might Sliver, but dont sleep on some of the grindier cards like Darkheart Sliver and Necrotic Sliver, the latter of which can find a home outside of tribal decks as well, like in a Karador, Ghost Chieftain build
While a dagger in the heart of a Morph deck, this card has got to be one of the bulkiest rares of all time at this point