Set Wars
The rules are simple:
-You can only use cards from ONE set, meaning all cards must exist in the same set, just as you would in draft. Remember that Set is different from Block in that a Block includes multiple sets. You should not, for example, have Journey Into Nyx cards in a Theros deck, unless that card was also printed in Theros.
-Do NOT make decks that are based on the yearly sets, such as M20, M19, etc. -Decks closely follow draft format deck size, meaning it can be as small as 40 cards, but should be no bigger than 60.
-There is a rarity limit in your deck, where you may only have up to 5 Uncommon, 3 Rare, and 1 Mythic. This is to set it apart from draft and also bring about a generally casual way to build a deck of this size. This really should not be an issue since you can only use cards from one set.
-Players start with 20 Hit Points, as is normal in draft.
-The community would have their own personal ban list of cards/sets that would be overpowered in this format, on top of the bans of cards such as Power Nine and other well-known Vintage cards that are rightfully banned in most formats.