Toxomister, called Puwazone (プワゾーン) in the Japanese Manual, is a Badnik from Sonic & Knuckles found in Lava Reef Zone. This badnik is a mechanical tube that produces a toxic cloud of mist that floats up (or down, depending on whether or not the badnik is on the ceiling). If Sonic or Knuckles touches the cloud, the cloud will stick on to him, making him lose rings at the rate of one a second and making his jump height decrease. If the cloud is on Sonic or Knuckles and he has no rings, he instantly loses a life. You can get rid of the cloud by spindashing. To destroy the badnik (which will also destroy the cloud), simply jump on the red eyeball atop the mechanical tube.
The mist can still stick onto the player and cause them to lose rings even when they are invincible, have a shield, or are in Super/Hyper form.
They return in Sonic Mania with the same attack pattern, again found in Lava Reef Zone.