Starting with a collection of all cards printed in sets from Zendikar and Innistrad, in particular with relation to the Eldrazi plotline (and a few other sets from those planes for support, cards from the Tarkir block, particularly Ugin's Fate, are free real estate since those are related even if we don't directly see the Eldrazi).

This will eventually be pared down to a 720 and tested.

Once that list is settled, it will probably be cloned and brought down to 540 and tested.

That process may repeat for 360, 240, and possibly 180.

These cards will then be given custom set symbols to mark which 'batch' they belong to for the sake of organization.