Mystical Teachings is a uncommon Instant card from Foundations (FDN), collector number 594. Current market price: $0.13, TCGplayer market prices via Scryfall.
Search your library for an instant card or a card with flash, reveal it, put it into your hand, then shuffle. Flashback {5}{B} (You may cast this card from your graveyard for its flashback cost. Then exile it.)