Art by Austin HsuPreDH is a sub-format of MTG, which excludes all cards printed after New Phyrexia.
Since this is an unseeded cube, all 360 cards are randomized and are dealt to players as 3 packs of 15 cards per pack. As a result, this cube can support up to 8 players. Players build 40-card decks, where 1 of the 40 must be their commander. In consideration of the size of the draft decks and the format, Brawl is used for play: players start with 25 life instead of 40, commander damage does not count, and players must pay a cumulative +2 mana tax each time they wish to recast their commander from the command zone. (This is technically an anachronism since Brawl was not created until after Pre-DH, but it optimizes gameplay.)
The rules of color identity apply to this cube. If a player wishes to play black and green, their commander must be a legendary creature that has at least both black and green in their color identity. Examples include Savra, Queen of the Golgari (who has black and green in the cost), Rhys the Exiled (who has green as part of the cost, and black as part of an activated ability), and Progenitus (who includes black and green as part of the five-color cost).
Commanders can be acquired through several means. Among the 360-card draftable cube, there are a number of mono-colored commanders. Any one of these can be used as a commander for a mono-colored deck of the same color.
Additionally, players will be provided a binder of 2-color, 3-color, and 5-color legendary creatures. At any time during the draft, for a max of 3 times, a player may "purchase" a legendary creature from the binder. To do so, a player must "trash" a number of cards that they have drafted whose color identity matches or exceeds the color identity of a legendary creature from the binder. Trashed cards are permanently removed from the draft. Purchased cards are revealed by the players that purchased them at the end of the draft. (I cannot take credit for the purchasing/binder draft feature, all credit goes to hedera.)
Example: A player wants to purchase Captain Sisay, a white green legendary creature listed in the binder. The player may trash a white Swords to Plowshares and a green Llanowar Elves to purchase Captain Sisay from the binder. Similarly, a player may trash a red green Stomping Ground and a white Swords to Plowshares for the purchase, using the Stomping Ground for its green color identity and Swords to Plowshares for its white color identity. A card with multiple color identities can only be used toward one color identity. As an example, the player trashes a white green Temple Garden to help purchase Captain Sisay. The player can then choose to trash Swords to Plowshares for the white, and use Temple Garden for the green.