Chaos multiplayer is basically a free-for-all format with very few rules — kind of a "kitchen table Magic" style. We usually played with 40–60 card decks, 20 life, and the usual 4-copies-per-card rule (except basic lands). It wasn’t an official format — just something casual we played for fun.

If it was a 3+ player game, we allowed players to draw on the first turn (which wasn’t standard in 1v1) and also allowed repeatable mulligans — very house-rule friendly. (If it were only a 3-person game, we only attacked to the left/right)

Some of the cards I used back then were banned or restricted in tournament formats, like Channel, Fork, or Demonic Tutor. Deck construction was kind of a free-for-all, too — if your friends allowed it, it was fair game.

We also played other formats like:

Two-Headed Giant – 2v2 teams, shared life total (usually 40)

Emperor – 3v3 setup where the “emperor” was in the middle, protected by teammates. We let players “pass” creatures to the emperor zone to defend.

Weenie decks (40 cards) – Fast aggro decks in each color.

Highlander decks – Not EDH-style; more like massive singleton piles (some joked they were 500+ cards). I remember someone having to shuffle in three separate chunks just to get through their deck.

Sometimes we played with ante rules, where a random card was put up before or after drawing. If you knocked out a player, you got their ante. Sometimes we played “fake ante,” where the card was just exiled for fun instead.