I have a vague memory of an unofficial Magic format from the 90's, that was similar in some ways to Planechase or Vanguard. In addition to the players' regular decks, there were cards that applied rules changes from "outside the game" ("command zone" by modern terminology), like Vanguards or Planes. A lot of the "command" cards were based on World Enchantments; some may have been based on other enchantments or artifacts with static abilities. I don't remember if each player picked one like Vanguard, or there was rotation like Planechase.
There was a site that listed the rules and had images of the "command" cards for making proxies. I saw it around 2001-2003, and it seemed a little old then.
Does anyone know what this format was called, or any extant sites with information about it?