This is the (probably not super strong) example deck for an original format: limstructed. The format uses 40 card constructed decks that have restrictions on rarity to make the decks proportioned somewhat close to draft decks. Rarity restriction also serves to keep decks affordable, it is easy to make a fairly strong deck for under $8 or so.
Deck building rules:
40 cards, all from the same set!
1 mythic, 1 rare, 7 uncommons, the rest commons or basic lands. Slots can be replaced by lower rarities, so a deck with 2 rares instead of a mythic and a rare is legal, as is a deck with 9 uncommons if it has no mythic or rare.
Rares must be unique, uncommons and commons must be at most 2x of the same card, with the exception that one common in the deck can be a 3x.
Sideboard is 7 cards, can be any distribution of rarities, but the deck must remain legal post-sideboarding, so if you pack your board with rares, you will only have 2 slots to swap them into.
The new nature of this format may break certain cards. For example, it's easier to mill a 40 card deck so it's likely that Hedron Crab will prove to be broken (especially with Archive Trap/Trapmaker's Snare in the same set). On this topic, during playtesting with an acquaintance at my LGs, I learned that Mirrodin's artifact lands, along with affinity for artifacts cards and strong accompaniment such as [Thoughtcast], [Frogmite], [Myr Enforcer], [Somber Hoverguard], [Psychic Membrane], [Vedalken Archmage], [Broodstar], etc. Again, this is not a properly existing format, and maybe a metagame would develop that would challenge this build, but seeing as these lands have been banned out of nearly every constructed format, I think it's safe to assume the artifact lands are out, and that this deck could potentially remain competitive without them!
