Shadows over Innistrad is a Magic: The Gathering expansion block consisting of the sets Shadows over Innistrad and Eldritch Moon. Shadows over Innistrad has five main mechanics: Madness: a returning mechanic from Time Spiral that allows a player to cast a card for its madness cost instead of being discarded. This is shown on the card Fiery Temper. Delirium: counts the number of different card types in a player's graveyard. If that player has four or more card types among cards in their graveyard (e.g. creature, instant, sorcery, land), delirium will grant specific effects or bonuses, like the card Soul Swallower. Investigate: a keyword that creates a Clue artifact token that you may pay 2 generic mana and sacrifice to draw a card, as seen on cards like Tireless Tracker. Transform: a returning mechanic from original Innistrad, allowing the card to "transform" to its back side if certain conditions are met, such as the card Westvale Abbey. Skulk: an evasion ability that appears on creature cards meaning that they can't be blocked by creatures with greater power, such as Rancid Rats.