Twenty Lessons is a uncommon Sorcery card from Unknown Event (UNK), collector number UA03. Current market price: $12.33, TCGplayer market prices via Scryfall.
Cast a random Lesson spell without paying its mana cost. If that spell has X in its mana cost, X is 3. (As of today, there are 20 lessons. Perhaps look up a list and roll a d20?)