Shadows over Innistrad: mechanics

Shadows over Innistrad set is on the way, hence it is high time to introduce new mechanics:

• double-faced cards. It is well known mechanic, however some rules changes take place with SOI prerelease. Since then, the converted mana cost of a flipped card is equal to the cost of the unflipped side. Well, it's relevant change and keep it in mind.
• Investigate: put a colorless Clue artifact token onto the battlefield with {2}, Sacrifice this artifact: Draw a card.
• Madness comes back from Torment / Time Spiral. It allows you to pay an alternate cost to cast a spell if it is discarded. It doesn't matter what its card type is, so for example you may cast creature with madness cost during yours opponent turn. The spell's mana cost and converted mana cost don't change. You're just paying the madness cost instead.
• Delirium: an ability word that gives an advantageous effect whenever there are four or more card types among cards in your graveyard. The card types that could show up in your graveyard are artifact, creature, enchantment, instant, land, planeswalker, sorcery and tribal.
• Skulk: a creature with skulk ability can't be blocked by creatures with greater power