1x1x1x1 (often called "The Adversary") is one of Roblox’s oldest and most infamous urban legends. Originally conceived in 2007 as a piece of fictional lore written by Roblox admin Shedletsky,

According to the official lore written by the Roblox staff, 1x1x1x1 was an ancient, malicious being from the fourth dimension. Because Roblox was built in three dimensions, 1x1x1x1 despised it.