When Will You Learn? is a common Scheme card from Archenemy: Nicol Bolas Schemes (OE01), collector number 20★. Current market price: $2.67, TCGplayer market prices via Scryfall.
When you set this scheme in motion, each opponent exiles the top card of their library. You may cast any number of spells from among cards exiled this way without paying their mana costs.