Shadows over Innistrad is a Magic: The Gathering expansion block consisting of the sets Shadows over Innistrad and Eldritch Moon.
Eldritch Moon features four returning mechanics from Shadows over Innistrad (all but Investigate) while introducing three new mechanics:
Meld: causes two separate creature cards to transform and combine into a single creature when certain conditions are met, creating an oversized card. Two such creatures that can Meld together are Bruna, the Fading Light and Gisela, the Broken Blade.
Escalate: An ability appearing on modal instant and sorcery spells. Paying the escalate cost allows the player to use additional modes of that spell, such as on Collective Effort.
Emerge: An ability appearing on powerful Eldrazi creature cards such as Elder Deep-Fiend, allowing players to pay an alternate mana cost by sacrificing a creature and paying the difference between the Emerge cost and the sacrificed creature's converted mana cost.