What are the key mechanics introduced in the Magic: The Gathering Shadows Over Innistrad set?

The Shadows Over Innistrad set introduced key mechanics like Delirium, Madness, Investigate, and Transform. Delirium rewards players for having different card types in their graveyard, Madness allows players to cast cards for a reduced cost when discarded, Investigate creates Clue tokens that can be sacrificed for card draw, and Transform allows certain cards to change into more powerful versions.