Deck built around doing things on your opponent's turn to try and take advantage of Endless Nightmare as a pressure point. The Influence is a bit tight if you're mostly playing sigils, especially for hitting Gentle Grazer, but Grazer is a major source of card advantage for you, so I'm not sure you can cut it.
I like Call for Aid in theory, but it might be better as Devour, especially with Endless Nightmare.
The market has Designs for combatting aggressive decks if they try to go around you.
Xenan Temple can shut down Vox decks.
Ebon Dune Smuggler into Dark Betrayal on turn 4 is really strong when facing ramp decks.
Pale Rider's Timepiece and Azindel are flex spots. I was also considering Dark Return, but usually Icaria coming down is strong enough on it's own. Timepiece is pretty good vs aggro and allows you to stabilize if you have a bit of a board presence.
(The three Rakano Icaria are standing in for new Shadow Icaria)