Cheerios is a combo archetype built around casting a large number of zero-mana cards, traditionally artifacts or Equipment. Those plentiful zeroes are used to trigger card-draw engines or other payoffs until the deck can assemble a winning sequence.
Bone Saw can get it all started as a free piece of Equipment, Puresteel Paladin keeps the cards flowing as more Equipment arrives, and then Retract scoops the whole arsenal back into your hand so you can potentially do it all over again.
