Siona, Captain of the Pyleas

Auras have spent most of Magic's history as a losing proposition: enchant a creature, and when that creature dies you have lost two cards to your opponent's one. This flips the math. Every time an Aura you control latches onto a creature you control, you get a body out of the deal, so the two-for-one built into enchanting quietly becomes a one-for-one plus a token. Enchant a fresh creature, get a Soldier; move an existing Aura to a new host, get another; recur one from the yard and reattach it, get another still. The trigger cares about the moment of attachment, not the moment of casting, so anything that reattaches or reanimates an Aura feeds the engine as readily as hardcasting one does. The enters-the-battlefield dig is the setup half: a look at the top seven to hold onto an Aura, so the commander that wants Auras also helps you find them. That is what elevates this past a role-player: it converts a whole class of historically underpowered cards into a token machine, the kind of build-around a legend in a two-color slot exists to justify. And the loop tightens as it runs, because the 1/1 tokens it makes become their own enchant targets, each new body another chance to fire the trigger the next time an Aura moves.