The Fog Roamer is a hostile mob found exclusively in the Foglands. It spawns only in the Fog, and only at night. If it leaves the fog, it will take constant damage. Its health and damage are similar to that of a zombie, however, it is much faster, and has a larger detection radius, as well as usually spawning in groups. Their danger comes from constantly ganging up on the player.
Fog Roamers appear as dark, shadowy humanoid figures with muted red eyes. They do not wield any equipment normally but can be spawned with it via console commands.
If the player is in an area with no fog, they will stand on the borders of the fog and stare at the player. If shot at (they will detect nearby projectiles even if not hit), fog roamers will walk backwards into the fog to hide themselves. Non-named Fog Roamers will run away from players and despawn in the daylight.
Despite their otherworldly nature, they are very "normal" mobs in that they do not have any particular resistances or weaknesses to any potion effects (IE: Zombies are immune to potions of harming, enderman cannot touch water).