To enable this surprisingly common scenario, all you need to do is have a sizable board in play
Chandra's Embercat Chandra's Firemaw Chandra's Flame Wave Chandra's Fury Chandra's Ignition a nasty damage-based board wipe that easily becomes a win condition with massive creatures or Stuffy Doll effects
But the charm lies in the second ability, which lets you proliferate and draw two cardstwo of the best game actions in a counter deck
Whether they have flying printed on them, gained flying before your Archetype of Imagination entered the battlefield, try to gain it after your Archetype of Imagination entered the battlefield, or are being granted flying continuously (say, by another Archetype of Imagination), they can't have flying for any reason while you control Archetype of Imagination
Under this paradigm, it becomes incredibly important to have a strong understanding of the relative power levels of every card in the Cube
Sometimes Pack Rat is much slower than you need it to be, but at other times it is the only card that can win you the game
