Once you have your lifegain creatures at work, Speaker of the Heavens can pump out a 4/4 angel token each turn, and Griffin Aerie can quickly make an army of 2/2 flyers
You may register 0-15 additional cards as your sideboard
There's not really any extra strong interaction between Choco and Keeper of the Nine Gales, but Choco wants to be attacking with as many birds as possible, so the basic synergy holds
Blightsteel Colossus Here comes the most feared and hated infect card in Magic: The Gathering: Blightsteel Colossus

(Bevy of Beebles) Bag of Devouring Bargaining Table Barrin's Codex Be'lakor, the Dark Master Bebop, Skull & Crossbones Become the Avalanche Bone Devourer Bound // Determined Bound // Determined Braingeyser Breakthrough Brilliant Spectrum Bruce Banner Camaraderie Cavalier of Flame Cerebral Download Champion of Dusk Chandra, Flamecaller Commence the Endgame Commodore Guff Contaminated Drink Corpse Augur Cosima, God of the Voyage Culmination of Studies Curse of Vengeance Cut of the Profits Dimir Strandcatcher Disciple of Bolas Disciple of Freyalise Disorder in the Court Diviner's Portent Dregs of Sorrow Elenda and Azor Elminster Elrond, Master of Healing Entreat the Dead Estinien Varlineau Even the Score Extraordinary Journey Finale of Revelation First Family Fruit of the First Tree Gadwick, the Wizened Gix, Yawgmoth Praetor Gix, Yawgmoth Praetor Graveborn Muse Graven Lore Greven, Predator Captain Hearth Elemental Hearth Elemental Hydroid Krasis Ill-Timed Explosion Illuminate Imskir Iron-Eater Ingenious Mastery Inscription of Insight Intelligence Bobblehead Invoke the Firemind Jace, the Perfected Mind

Let blue decks or black decks play Ashiok, and there will be a mountain of decks that slot Ashiok in because their pilots feel like they can't afford not to