Nahiri's plan for revenge on Sorin Markov comes to fruitition. Using the Drownyard and the loss of Avacyn, she has coaxed the Eldrazi titan Emrakul through the Blind Eternities to Innistrad.
Emrakul is the Titan of Corruption, the largest and most fearsome of the Eldrazi. She does not affect unliving matter - rocks, water, etc... but twists all things living, be it plants, animals, or sentient beings. She causes silent terror wherever she soars, embodying desolation, emotional and physical distance, the chill of the void, and the terror of being alone.
The Emrakul lineage is characterized by fleshlike lattice structures, uneasy bilateral symmetry, and tentacles that end in knobby, vestigial digits. Looking like spongy, alien baleen, the lattice respires independent of the Eldrazi itself, supporting a host of unseen mite-creatures within.