Maro said: no subgames in black border due to tournaments.
So I decided to write down a subgame cycle
Proof of planning
Sorcery
play a subgame using each player battlefield as the battlefield, your opponent starts, players can't draw cards, creatures have haste and it lasts one turn. Before the end of the subgame, return everything to the battlefield, then if you didn't take combat damage that turn, create an artifact token with "Creature you control gain +2/+2" and "
creatures lose defender until end of turn" in the main game.
Examine the future
Sorcery
Exile cardname, then play a subgame using each player library, you start, you have a treasure for each land you controlled as you started the subgame and can't start new subgames, it last one turn. At the end choose up to 3 cards in your hand and add them to your real game hand, and shuffle the rest of the used cards into their owner library.
The World of the dead
Sorcery
Play a subgame using each player's graveyard as library, players don't lose from drawing from an empty library and can pay 1 life to add 1 mana of any color. it lasts 6 turns. At the end, return to the main game and return everything to the graveyard, and the player with the lowest life total banishes it's graveyard,then if a player died, banish their hand. You may then return up to 2 creature cards from your graveyard to the battlefield.
Threaten the younger self
Sorcery
Play a subgame using the top 7 cards of each player library, you start, players can't draw outside their starting hand and it ends at the end of the third turn. at the end, reshuffle the used cards into each library, then players gain or lose life equal to the life they gained and lost in the subgame.
Assault on another front
Sorcery
Play a subgame using each player's hand, you start, players can't lose by deckout and it ends at the end of the first turn, creatures in your hand have haste and cost
, creatures in your opponent hand have flash and cost
.At the end, return each used card to it's owner hand then players gain or lose life equal to the life they gained and lost in the subgame.