It isnt a mechanic that does anything on its own, but if you have Lessons in your sideboard, you can get them during the game using any card that says Learn. In other words, when you have a card that has a Learn effect, you get to look at your sideboard and select any card that has the Lesson subtype
This is great for decks that use Area Zero Underdepths, as they have a reliable Tera Pokmon that doesnt immediately get KOd
Getting 3 coloress mana to cast artifacts is literally no drawback if you are playing a lot of artifacts anyhow, which is why this card gets played in playsets in Vintage
Good King Mog XII last looked out, on a board of Moogles, lifelink tokens lay around about, populating not frugal, Dont be so quick to dismiss, the chapters in the middle, Take advantage and copy your board, then youll solve this riddle