As you cast a tiered spell, you choose one of its modes to play and pay the associated additional cost to do so
For example, let's look at Environmental Sciences, one of the simplest Lesson cards
If this kind of strategy attracts you, then give it a go
But now, even as the memories of battle have begun to fade, a new evil grows inside Vana'diel
Its efficient enough that you can play it in Rakdos sacrifice decks in many formats and in artifact-based EDH decks
Commander Masters is coming to Magic: The Gathering stores on August 4, but in keeping with Magic tradition, Wizards of the Coast has treated us to the full decklists including all the new cards that will be coming in the four preconstructed decks