Gaseous Tenebrae[]
Gaseous Tenebrae is an Item from Thaumic Tinkerer, which is a plugin mod for Thaumcraft 3. Gaseous Tenebrae can be made like every other thaumcraft items. However, you have to research it first.
Gaseous Tenebrae, when used, will darken an area and have some cool particle effects. To remove the gaseous tenebrae, Shift-Right click while you have the Fume Dissipator in your hand.
It also seems to turn Grass Block/Mycelium into dirt