Roon of the Hidden Realm – blink your own creatures for extra enter-the-battlefield value, and use his ability with instant-speed interaction (like Tale’s End or Repudiate) to permanently exile your opponents’ commanders by stopping them from returning to the battlefield, completely removing them from the game!
Frilled Mystic – counterspells on a stick to keep your opponents honest
Watcher for Tomorrow and Archaeomancer – find key spells and reuse them over and over
Aid from the Cowl – extra land ramp and value with each permanent’s ETB triggers
Momentary Blink and Displace – instant-speed blink tricks to surprise opponents and get more ETB triggers
