Can be found anywhere outside of Protection Zones, but more common in swampy areas.
Notes:
By stepping on these you get the Poisoned status and take 5 points of damage on contact, and will lose damage over time, starting at 5 Damage (4x5+5x4+7x3+10x2+19x1=100 total damage). Its effects can be cured by the Antidote spell or Antidote Runes and the gas removed by Destroy Field Rune