An infinite mana combo to possibly add. Exile Sleep-Cursed Faerie with Agatha's Soul Cauldron (already in the cube) and put two +1/+1 counters on Kami of Whispered Hopes to produce unlimited mana of any color. Realm-Scorcher Hellkite offers an outlet for all that mana, and Seed of Hope and Wasteful Harvest can dig to find the pieces.